_Progress of Science in the Eighteenth and Nineteenth Centuries._
SECTION I.
_Physical Science._
IT should be understood that the aim of this chapter is not to present a history of science, but chiefly to indicate what Scotland has contributed to the science of the period, and to show the importance of science as a factor in advancing civilisation. It will, therefore, in the first place, touch on the significance and progress of mathematical science; in the second, on physical science, or natural philosophy; and in the third, on mechanical science, or science in relation to its practical application.
From an early period various conceptions of the universe have been entertained; even Newton’s conception of it and his system founded on the theory of gravitation are not quite satisfactory. Hence his followers for a long time mainly occupied themselves in defending and explaining his system; they were loth to recognise that either his method or system was susceptible of improvement or extension――they adhered to his conclusions with extreme tenacity and superstitious veneration. While, in other parts of Europe, Descartes’ theory of the universe held the field, the earliest recorded recognition of Newton’s principles in France was in a memoir by Lonville, which appeared in a volume of the _Academy of Sciences_ for the year 1720; and the first French astronomer who ventured on a defence of the theory of gravitation was Maupertius, in his work on the figures of the celestial bodies, published in 1732. He compared the theories of Descartes and Newton, and came to a conclusion in favour of the latter. It was Voltaire, however, that really diffused a knowledge of Newton’s system in France, by the publication, in 1738, of his clear exposition of Newton’s discoveries in optics and astronomy. Henceforth in France the Newtonian system prevailed over the theory of Descartes.
The controversy touching the priority of the invention of the calculus between Newton and Leibnitz was an unfortunate affair, as it arose from trivial incidents. In short, from the first Leibnitz admitted Newton’s priority in forming the conception of the calculus; but he maintained, what was doubtless true, his own originality in the invention of the differential calculus. This branch of mathematical analysis was not much advanced by Newton and the English geometers of his time; as Newton himself was fond of geometrical forms and the synthetical method of statement. His treatise on _Fluxions_ was not published till after his death in 1736. When, however, it became known that the differential calculus was rapidly circulating on the Continent――and so little was Newton’s method known, that Leibnitz was regarded throughout Europe as its original inventor――the followers of Newton began to feel that this impression was unjust towards their great teacher, and hence the bitterness of the controversy which ensued. The result was a wide alienation between the English and foreign mathematicians, which had a pernicious effect on science. “Each party became the exclusive supporters of the two great luminaries of their respective countries. The British mathematicians, in particular, adhered with the most rigid pertinacity to the very letter of Newton’s methods; and were, with few exceptions, completely ignorant both of the original investigations of the other party, and of the improvements upon them which were being rapidly introduced.
“The difference in name and notation between the two methods, though in itself a trivial circumstance, was yet far from unimportant in some of the consequences which may be fairly traced to it. It tended in some measure to foster and increase the dissension between the two schools, and their ignorance of each other’s researches; while the diversity itself between the two methods, though in reality little more than nominal, became also a topic of no small dispute and controversy. But much as these differences were on all grounds to be lamented, the loss in point of scientific advantages, it must with shame be confessed, were almost entirely on the side of Britain.”1
1 Powell’s _History of the Physical and Mathematical Sciences_, page 363. 1834.
If we reflect upon the past three centuries and ask what were the most requisite means of aiding men in their investigation of nature and the explanation of the phenomena of the universe, the answer must be mathematical science. In astronomy and in other branches of physical science, mathematics are indispensable; for as the universe exists in space and time――the two concepts which encircle all things――so it is a universal truth, that mathematics are not only the prime requisites in physical science, but also essential elements in navigation, engineering, shipbuilding, architecture, and in many other arts.
In the early part of the eighteenth century Scotland produced one eminent mathematician――Colin Maclaurin1――and several others of lesser note. He was a native of Kilmodan, in Argyleshire, a son of a clergyman, was educated at the University of Glasgow, and early manifested an aptness for mathematics. In 1717, before he had attained his twentieth year, he was elected, after a ten days’ competition, Professor of Mathematics in Marischal College, Aberdeen; but in 1725, he was appointed assistant and successor to Dr. Gregory in the Chair of Mathematics in the University of Edinburgh. It is recorded that he was an able and successful instructor, and that in his public teaching he clearly explained the application of his science to purposes of utility and the perfecting of the mechanical arts.2
1 Born in 1698; died in 1746.
2 He soon became the leading spirit in the University of Edinburgh, and the celebrity which the Chair of Mathematics had attained under the Gregories was admirably sustained and even extended by him. In the _Scots Magazine_, in 1741, a full programme of Maclaurin’s courses of academical instruction is given as follows:――“He gave every year three courses, and sometimes a fourth, upon such of the ♦abstruse parts of the science as were not explained in the former three. The first course contained――Demonstrations of the ground of Vulgar and Decimal Arithmetic; six books of Euclid; Plane Trigonometry and use of the tables of Logarithms, Sines, etc.; Surveying, Fortification, and other practical parts; the Elements of Algebra; and a lecture on Geography once a fortnight.
“The second course consisted of――Algebra; the Theory and Mensuration of Solids; Spherical Trigonometry, the doctrine of the Sphere, Dialling, and other practical parts; Conic Sections, with the theory of Gunnery; the Elements of Astronomy and Optics. He began the third course with Perspective; then treated more fully of Astronomy and Optics. After this he prelected on Sir Isaac Newton’s Principia, and explained the direct and inverse method of Fluxions. At a separate hour he gave a course of Experimental Philosophy, beginning about the middle of December, which continued thrice every week till the beginning of April; and at proper hours of the night he described the constellations, and showed the planets by telescopes of various kinds.” This was a comprehensive course of teaching. He also exerted himself to the utmost to provide an Observatory for the instruction of students in the University of Edinburgh, and would have been successful but for his early death. Although the foundation of an Observatory was laid in Edinburgh by the Town Council and Senatus, on the 25th June, 1776, it was not until 1834 that the Observatory was rendered available for the practical instruction of students of the University.
It has been said that in “Maclaurin’s time the teaching of mathematics reached a point which it cannot be said to have yet surpassed.”――Sir A. Grant’s _Story of the University of Edinburgh_, Volume II., page 299.
♦ “abtruse” replaced with “abstruse”
His works are these:――(1) _Geometrica Organica_; (2) _A Complete System of Fluxions_; (3) _Treatise on Algebra_; (4) _Account of Sir Isaac Newton’s Philosophy_; (5) Various elegant and ingenious papers published in the _Transactions of the Royal Society_; and (6) _A Memoir on the Tides_.
In connection with his _Memoir on the Tides_, written in 1740, he gained equal honour with Euler and Daniel ♦Bernoulli, a famous Italian mathematician, as the prize of the French Academy of Sciences was equally divided among them. All the three adopted the principle of gravitation as the basis on which they attempted to explain the phenomena of the tides; and the results which they arrived at, presumed the earth to be at rest and the waters of the ocean also, and at every moment in a state of equilibrium between the force of gravity tending to the earth’s centre, and the lesser forces tending towards the sun and moon. This view is known as the equilibrium theory; and though it is far from perfect, it correctly indicates a part of the phenomena of the tides, notwithstanding that the problem of the tides is a dynamical and not a statical one. Subsequently the important subject of the tides was treated at great length by Laplace, but unfortunately his tidal theory was so profound that very few men have ever attempted to master its difficulties. The late Mr. Airy, the Astronomer Royal, however, gave to the public a connected and clear view of it.1
♦ “Bernouilli” replaced with “Bernoulli”
1 Mr. Airy summed up the merits of Laplace’s theory thus:――“If, putting from our thoughts the details of the investigation, we consider the general plan and objects, we must allow it to be one of the most splendid works of the greatest mathematician of the past age. To appreciate this, the reader must consider――first, the boldness of the writer who, having a clear understanding of the gross imperfection of the methods of his predecessors, had also the courage deliberately to take up the problem on grounds fundamentally correct, however it might be limited by suppositions afterwards introduced; secondly, the general difficulty of treating the motions of fluids; thirdly, the peculiar difficulty of treating the motions when the fluids cover an area which is not plane but convex; and fourthly, the sagacity of perceiving that it was necessary to consider the earth as a revolving body, and the skill of directly introducing this consideration. The last point alone, in our opinion, gives a greater claim for reputation than the boasted explanation of the long inequality of Jupiter and Saturn.”――_Encyclopædia Metroa_, “Tides and Waves,” Article 117; compare Grant’s _History of Astronomy_, page 71, _et seq._
After Laplace, the theory of the tides has been treated by Dr. Thomas Young; and Dr. Whewell and Sir John Lubbock were engaged for many years in determinating the laws of the tides by observation, and in tracing their connection with the positions of the sun and moon. The chief results of their researches were published from time to time in a series of papers, in the volumes of the _Royal Society_.
Maclaurin also entered the arena in defence of the Fluxional system, which was boldly attacked by Berkeley, the famous Idealist, in _The Analyst_, published in 1734. Berkeley argued that the fundamental idea of supposing a finite ratio to exist between terms absolutely evanescent is completely absurd and unintelligible, and with biting sarcasm called these ratios “the ghosts of departed quantities.” Dr. Irwin produced a reply, and several others appeared on both sides; but Maclaurin and Robins made the most satisfactory defence of the principle of limiting ratios. Still the point was not thoroughly cleared up, till D’Alembert showed the real application of the principle of limits in the simplest form; and at last Lagrange, in his theory of Functions, discarded all idea of infinitesimals and limits, and reduced the whole to a simple algebraical investigation, by the development of functions in series.
Maclaurin’s method and style in the solution of problems were greatly admired. He showed in his applications of mathematics to physical problems a rare power of seizing the really important points amidst a mass of irrelevant details. In private life he was one of the best and worthiest of men.
James Stirling,1 another distinguished Scottish mathematician, was a native of Stirlingshire. He was educated at the University of Glasgow, and afterwards on Snell’s foundation at Oxford. While studying at Oxford, he printed, in 1717, a small tract on “lines of the third order, with new solutions of some difficult problems by the fluxionary calculus.” Subsequently he accepted an invitation to settle at Venice, where he remained for several years and taught mathematics.
1 Born about the end of the seventeenth century, and died in 1772.
Having returned home, he opened a mathematical school on Tower Hill, and maintained a correspondence with philosophers at home and abroad. In 1730, he published his well-known work on _The Differential Method and Series_. After toiling in his school for several years, he was induced to leave London, and undertake the direction of the mines at Leadhills in Scotland. In that elevated region, near Sanquhar, he resided during the rest of his life; and by his skill, intelligence, and energy, greatly improved the operations of extracting the lead ore. He now held a good position; but his high mathematical fame would have secured to him the honour of succeeding Maclaurin in the chair of mathematics in Edinburgh, in 1746, if he had not at that unhappy time been tainted with Jacobite opinions.1 In his later years he seems to have confined himself to practical concerns.
1 Leslie’s _Dissertation for the Encyclopædia Britannica_.
Matthew Stewart was elected to the vacant chair of mathematics in Edinburgh. He was a mathematician of note in the department of geometry; and is the author of _Tracts, Physical and Mathematical_. Robert Simson, who long held the chair of mathematics in the University of Glasgow, was a distinguished geometer. The names of Playfair and Leslie may also be mentioned as distinguished professors and learned mathematicians.
Passing to physical science, it is necessary to observe that in the eighteenth century the several branches of this department were not then so clearly distinguished from each other as they are now. The subject of heat was treated as a branch of chemistry; while chemistry itself was usually conceived as a mere appendage to medicine. Dr. Cullen was the first in Britain who assigned to chemistry its proper place as a science.
Dr. Black, the eminent professor of chemistry, and the discoverer of latent heat, was born in France, in 1728, where his father was then engaged in the wine trade. He received the rudiments of his education at Belfast; and in 1746, he entered the University of Glasgow, and under Dr. Cullen, was instructed in the science of chemistry, in which he showed much aptitude. As he intended to follow the medical profession, he went to Edinburgh to complete his studies, and graduated in 1754. Before this, he had prosecuted a series of chemical experiments touching the causticity of many earthy bodies, which resulted in his first discovery of the existence of fixed air or carbonic acid gas as an essential constituent of marble and other solids, along with a train of important consequences.
In 1755, Dr. Cullen removed to Edinburgh, and in 1756, Dr. Black succeeded him as professor of medicine and chemistry in the University of Glasgow. At this time he directed special attention to the subject of heat. He had discovered the phenomenon of “Latent Heat” at least as early as 1758, and taught the doctrine in his lectures at Glasgow.1 He was the first who formed distinct ideas on the subject.
1 Dr. Black himself, writing in 1780, said:――“I began to give the doctrine of latent heat in my lectures at Glasgow, in the winter 1757‒58, which I believe was the first winter of my lecturing there, or, if I did not give it that winter, I certainly gave it in 1758‒59, and I have delivered it every year since that time in my winter lectures, which I continued to give at Glasgow until winter 1766‒67, when I began to lecture in Edinburgh.”――Letter of Dr. Black to Mr. Watt, 1708, quoted by Muirhead in his _Life of James Watt_, pages 309‒310.
He deduced the discovery of latent heat from experiments showing that ice in being melted absorbs 140° of heat, which becomes latent in the water produced, thus:――“The melting ice receives heat very fast, but the only effect of this heat is to change it into water, which is not in the least sensibly warmer than the ice was before. A thermometer, applied to the drops or small streams of water, immediately as it comes from the melting ice, will point to the same degree as when it is applied to the ice itself.... A great quantity, therefore, of the heat, or of the matter of heat, which enters into the melting ice, produces no other effect but to give it fluidity, without augmenting its sensible heat; it appears to be absorbed and concealed within the water, so as not to be discoverable by the application of a thermometer.”1 By comparing the time required to change the ice from 28° to 32°, with the subsequent time required for its complete liquefaction, he found that it absorbed about 140 times as much heat as would raise its temperature one degree; and he also found that one pound of ice, when mixed with one pound of water, was just melted, but not raised in its temperature above 32°. So he concluded that water differed from ice of the same temperature by containing a great quantity of heat or the cause of heat, which would not quit it for another colder body, nor go into the liquor of the thermometer and expand it. This phenomenon, considered as the possible cause of heat, was latent, and Black accordingly called it “latent heat.”2
1 Black’s _Lectures on the Elements of Chemistry_, Volume I., page 119. 1803.
2 Black’s _Lectures on the Elements of Chemistry_, Volume I., pages 120‒132.
This discovery was connected with his experiments and researches on boiling and evaporation, which ultimately resulted in laying the foundation of the practical application of steam. He concluded that a great quantity of heat becomes latent during the conversion of water into vapour or steam; and he endeavoured to determine this quantity by experiment. He found that the latent heat in steam, which balanced the pressure of the atmosphere, was upwards of 800°. He also directed Dr. Irvine of Glasgow, one of his own pupils, to make an experiment for measuring the heat actually extricated from steam during its condensation in the refrigeratory of a still, which was found to be 774°. A few weeks after, Mr. James Watt made similar experiments on steam with a similar still; and the medium result of these trials gave 825°.1 It may be observed that, in these early experiments, the latent heat of steam was considerably underrated.
1 _Ibid._, pages 144‒174. I deem it of interest to give a few brief quotations from Dr. Black’s lectures on the latent heat of steam, to indicate his views. “I immediately set about boiling off small quantities of water, and I found that it was accomplished in times very nearly proportional to the quantities, even although the fire was sensibly irregular.
“My conjecture, when put into form, was to this purpose: ――I imagined that during the boiling, heat is absorbed by the water, and enters into the composition of the vapour produced from it, in the same manner as it is absorbed by ice in melting, and enters into the composition of the produced water. And, as the ostensible effect of the heat, in this last case, consists not in warming the surrounding bodies, but in rendering the ice fluid, so in the case of boiling, the heat absorbed does not warm surrounding bodies, but converts the water into vapour. In both cases, considered as the cause of warmth, we do not perceive its presence: it is concealed, or latent, and I give it the name of Latent Heat....
“I put into a very strong phial about as much water as half filled it, and I corked it close. The phial was placed in a sand-pot, which was gradually heated, until the sand and the phial were several degrees above the common vaporific point of water. I was curious to know what would be the effect of suddenly removing the pressure of the air, which is well known to prevent water from boiling. The water boiled a very short while, but the ebullition gradually decreased, till it was almost insensible. Here the formation of more vapour was opposed by a very strong pressure proceeding from the quantity of vapour already accumulated and confined in the upper part of the phial, and from the increased elasticity of this vapour, by the increase of its heat. When matters were in this state, I drew the cork. Now, according to the common opinion of the formation of vapour by heat, it was to be expected that the whole of the water would suddenly assume the vaporous form, because it was all heated above the vaporific point. But I was beginning by this time to expect a different event, because I could not see whence the heat was to be supplied, which the water must contain when in the form of vapour. Accordingly, it happened as I expected: a portion only of the water was converted into vapour, which rushed out of the phial with a considerable explosion, carrying along with it some drops of water. But, what was most interesting to me in this experiment, was, that the heat of what remained was reduced in an instant to the ordinary boiling point. Here, therefore, it was evident that all that excess of heat which the water had contained above the boiling point, was spent in converting only a portion of it into vapour. This is plainly inconsistent with the common opinion, that nothing more is necessary for water’s existing in a vaporous form under the pressure of the atmosphere, than its being raised to a certain temperature....
“This experiment was afterwards made by my friend Mr. Watt, in a very satisfactory manner. His studies for the improvement of the steam-engine gave him a great interest in everything relating to the production of steam.”――Pages 159‒160.
In 1781, Dr. Black said to the students of his class:――“I think it sufficient to inform you that Mr. Watt, in the course of his studies on the steam-engine, has made all the necessary experiments with the most scrupulous care, knowing that the improvement of that noble engine must depend entirely on an exact knowledge of the procedure of nature in the formation and condensation of steam. Mr. Watt informs me that he has observed as exact coincidence between the heat rendered latent in the vapour, and that which emerges from it, as can be desired; and that the heat obtainable from steam, capable of sustaining the ordinary pressure of the atmosphere, is not less than 900° of Fahrenheit’s scale, and that it does not exceed 950°.”――_Ibid._, page 174.
Dr. Black also contributed to advance the knowledge of Specific Heat; but he chiefly left the development of this branch in the hands of his pupil Dr. Irvine, who was professor of chemistry in the University of Glasgow from 1769 to 1786, and to Mr. Watt, for both of whom he had the greatest respect.
In 1766, Dr. Black was appointed professor of chemistry in the University of ♦Edinburgh, in succession to Dr. Cullen; and he filled this chair with much credit to himself and advantage to the University, until his death in 1799. He was a very successful instructor; his lectures in the class-room were described by those who heard them as inimitable, and so interesting that they never failed to rivet attention.1 Thus his influence on the progress and the diffusion of science by his teaching for the long period of forty-three years, and his intercourse with society, was great and highly beneficial to his country and to the world.
♦ “Ediuburgh” replaced with “Edinburgh”
1 Professor Robson, one of his pupils, and the editor of his lectures, says that Dr. Black endeavoured every year to make his course of lectures more plain, and illustrated them by more examples in the way of experiment. So the students in his class “were not only instructed, but delighted; and he became a favourite lecturer, and many were induced, by the report of his students, to attend his courses.”
Another branch of the science of heat was taken up by Sir John Leslie;1 he directed his attention to “Radiant Heat”――heat propagated from hot bodies to sensible distances. Sir John was educated at the University of St. Andrews, and early manifested a bent for mathematical studies. His work on the _Nature and Propagation of Heat_, which appeared in 1804, first brought him into notice; and the following year he was appointed to the chair of mathematics in the University of Edinburgh.
1 Born in 1766, and died in 1832.
The fact that heat is radiant, passing through space like light, was known at an early period; and various experiments had been made, and some of the phenomena which characterise it indicated; but heat in its radiant form was not systematically investigated till towards the end of the eighteenth century. The band of scientific men then engaged on this subject were Pictet, Prevost, Rumford, and Herschel; the first two were professors in Geneva, and were earlier in the field than Leslie. In 1791, Pictet’s work entitled _Essai sur le Feu_ appeared, which contains observations on latent and specific heat, and on the power of different surfaces to reflect and absorb it. He showed that radiant heat moves with great velocity. His treatise also embraced observations on hygrometry, on various points of meteorology, and on friction heat. He has the merit of establishing the meteorological observations at the convent of the Great St. Bernard, and thus commenced a series which has proved exceedingly interesting to scientific men.
Prevost is the author of the theory termed the “Movable Equilibrium of Heat.” His fundamental idea is that heat is a substance related with bodies of a highly elastic nature, continually given off from them in proportion to their temperature, which may represent the tension of the imaginary elastic fluid. Thus, when the temperature of a body is stationary, it is because it receives by radiation from surrounding bodies exactly as much heat as it parts with in the same way.1 His views were first published in 1791.
1 Dr. Forbes’s _Dissertation for the Encyclopædia Britannica_, page 944. 1856.
Leslie was an ingenious and able experimenter. But unfortunately he started his researches with some rather dogmatic preconceptions; he had a notion that the pressure of air is essential to the propagation of heat; nevertheless, many of his experiments are interesting and valuable. He used a thermoscopic instrument constructed by himself, which he called the differential thermometer; it is an ingenious modification of the common air thermometer. He showed that the radiating or emissive effect of different surfaces varied from 100° to 12°. He also showed by experiment that the radiation of heat from a plane surface proceeds with unequal force in different directions. When the specific heating power of the colorific rays is measured in a direction perpendicular to the surface whence it emanates, it is found to be at a maximum; and at any other angle with the surface, it varies as the sine of the angle. Afterwards this was also found to prevail in the case of light. His experiments to prove that the law of radiation of heat varies inversely as the square of the distance were not quite conclusive.
He considered the influence of colour on the heating of bodies by original experiment; and it was found to be effectual only when the radiations were luminous. He engaged in long and ingenious researches touching the law of cooling bodies, embracing the effects of mass, surface, contact of air, currents of air, the cooling effects of different gases, and of air of different degrees of rarefaction.
Besides his work on heat, his _Dissertation on the Progress of Physical and Mathematical Science_, and the articles on “Cold” and “Meteorology,” in the seventh edition of the _Encyclopædia Britannica_, he is the author of _Elements of Natural Philosophy_ (left unfinished), a _Treatise on Geometry_, and _Philosophy of Arithmetic_.
He held the mathematical chair from 1805 to 1819, and in the latter year he was appointed to the chair of natural philosophy. He had a large and fine collection of apparatus, as indicated above, and devised many ingenious experiments. He was elected a corresponding member of the Institute of France in 1820; and, on the recommendation of Lord Brougham, he received the honour of knighthood in 1832.
Since Leslie’s time the science of heat has been greatly advanced; the dynamical theory of heat has been developed in the present century, and Scotsmen have contributed their share to the definite advancement of this branch of science. But it has been advanced to its present stage by a long list of scientific men. In 1812, Davy enounced that the direct cause of the phenomenon of heat is motion, and that the laws of its communication are precisely the same as the laws of the communication of motion. The researches into the radiation and absorption of heat mainly form the physical basis of Spectrum Analysis, which has greatly extended the power of ascertaining the constituent elements of the celestial bodies, the sun and the fixed stars.
In the researches which ultimately led to these results, several Scotsmen have taken an honourable part. Professor Forbes discovered and demonstrated the polarisation of heat, and thus showed that radiant heat and light are the same. Among others who have contributed to advance Spectrum Analysis, I may mention Professor Stokes, Professor Balfour Stewart, and Sir William Thomson, of the University of Glasgow. Sir William Thomson (now Lord Kelvin) has taught the doctrine that there is sodium vapour in the sun’s atmosphere, in his public lectures in the University of Glasgow, since the year 1852.
Interesting conclusions touching the composition of the sun and of some of the stars have been reached:――“When we compare the spectra of different stars with that of the sun, we come to some very curious conclusions. We find four classes of spectra, as a rule, among the different fixed stars which have seemed of importance enough to be separately examined. The first class of spectra are those of white stars. You see an admirable example in Vega, and another in Sirius or the dog-star. All these white stars have the characteristic that they have an almost continuous spectrum with few dark lines crossing it, and these for the most part lines of hydrogen. These stars are in all probability at a considerably higher temperature than the sun. Then you come to the class of yellow stars, of which our sun is an example. In their spectra you have many more dark lines than in those of the white stars, but you have nothing of the nature of nebulous bands crossing the spectrum, such as you find in the third class; still less have you certain curious joins of shaded lines which you have in the fourth class of stars. This classification seems to point out the period of life, or phase of life, of each particular star or sun. When it is first formed, by the impact of enormous quantities of matter coming together by gravitation, you have very nearly continuous spectrum of a glowing white-hot liquid or solid body, or it may be dense gas, the sole, or nearly sole, absorbent being gaseous hydrogen in comparatively small quantity, and the spectrum having therefore few absorption lines. As it gradually cools, more and more of these gases surrounding its glowing surface become absorbent, and so you have a greater number and variety of lines. Then, as it still further cools, you have those nebulous bands which seem to indicate the presence of compound substances; which could not exist in the first two classes, because their temperature is so high as to produce dissociation. Still further complexity of compounds will be found in the atmosphere of the fourth class.”1
1 _Recent Advances in Physical Science_, by P. G. Tait, pages 230‒231.
After the publication of Newton’s _Optics_ in 1704, the history of this branch of science was almost a blank in Britain, till 1803, when the researches of Dr. Young on the undulatory theory of light appeared; and since the subject has been treated with increasing interest and success.
Sir David Brewster,1 who attained distinction in this branch of science, and in other fields of intellectual effort, was a native of Jedburgh. He was educated at the University of Edinburgh, and had the advantage of the instruction of Professor Robison, and other eminent teachers who then spread the rays of light with consummate ability. He devoted himself to science; and in 1805, he edited Ferguson’s _Lectures on Astronomy_; and, as already mentioned, he commenced the _Edinburgh Encyclopædia_ in 1810. His first separate work, _On New Philosophical Instruments_, appeared in 1813, which also contained observations on refractive and dispersive powers. From this date onwards he became a regular contributor to the London Philosophical _Transactions_, and also those of Edinburgh; he commenced the _Edinburgh Philosophical Journal_ and the _Edinburgh Journal of Science_. His contributions to scientific societies and journals would fill many volumes. One list of his scientific papers extends to the number of three hundred and fifteen, and the following is only the briefest indication of some of the more important subjects treated in them:――
1 Born in 1781; died in 1868.
(1) “The Laws of Polarisation by Reflection and Refraction, and other Quantitative Laws of Phenomena;” (2) “The Discovery of the Polarising Structure induced by Heat and Pressure;” (3) “The Discovery of Crystals with Two Axes of Double Refraction, and many of the Laws of their Phenomena, comprising the Connection of Optical Structure and Crystalline Forms;” (4) “The Laws of Metallic Reflection;” (5) “Experiments on the Absorption of Light.”
The more important of his other works are――(1) _A Treatise on the Kaleidoscope_, published in 1819; (2) _A Treatise on Optics_, 1831; (3) _A Treatise on the Microscope_; (4) _A Treatise on the Stereoscope_; (5) an Article on “Magnetism,” reprinted from the _Encyclopædia Britannica_; (6) _The Martyrs of Science――Galileo, Tycho Brahe, and Kepler_; (7) _Life of Sir Isaac Newton_; (8) _Letters on Natural Magic_; (9) _More Worlds than One_. He also wrote a _Life of Euler_ and edited his Lectures; edited Robison’s _System of Mechanical Philosophy_, with a preface and notes, which appeared in 1822, in four large volumes; he also contributed seventy-four articles to the _North British Review_.
This enumeration of his writings, though far from complete, is sufficient to show his great mental energy, and his scientific and literary talents. He was a man of remarkable intellectual resource, his imaginative and elaborative faculties were of a high order, and, for industry and observation he has rarely been surpassed. His style is clear and flowing, he has a copious command of expressive language.
Besides his discoveries of the law of polarisation, of biaxal crystals, of optical mineralogy, and of double refraction by compression, he invented a dioptric apparatus for the illumination of lighthouses, which he described in 1812. In 1820, he endeavoured to get the dioptric system adopted, but failed; at length, however, on the motion of Mr. Hume, a Committee of the House of Commons was appointed to consider the subject; and, in 1836, this system was applied to a Scotch lighthouse, and has since been universally extended. In 1816, he invented the kaleidoscope, which soon became popular over Europe; afterwards, he made an important improvement on the principle of constructing stereoscopes. In the words of Professor Forbes――“Few persons have made with their own eyes so vast a number of independent observations; few have ever observed better, or recorded their observations more faithfully.” He was an honour to his country and a benefactor to mankind.
In the interesting science of the earth――geology――Dr. Hutton, in 1788, enounced his theory that the changes in the earth’s crust have been mainly caused by the agency of fire; but though his views were ingenious and well argued, they have long ago been superseded by conclusions more in accordance with the observed phenomena. This branch of knowledge has been much investigated in the present century, and several Scotsmen have attained distinction in advancing it.
Sir Charles Lyell1 was a native of Forfarshire, and studied at Oxford. His _Principles of Geology_, being an attempt to explain the former changes of the earth’s surface by a reference to causes now in operation, appeared in 1830‒32, in two volumes. He made additions to it, and alterations from time to time, and the eighth edition of the work, thoroughly revised, was published in 1850. Though he recognised new facts, he continued to hold his theory that we may dispense with sudden and general catastrophes, and consider the past and present fluctuations of the organic and inorganic world as forming one continuous and regular series of phenomena.
1 Born in 1797; died in 1875.
In 1838, he published his _Elements of Geology_, which was afterwards enlarged to two volumes. He is also the author of _Travels in North America, with Geological Observations on the United States, Canada, and Nova Scotia_, published in 1845. He was twice elected president of the Geological Society, and he received the honour of knighthood in 1848. His style is attractive, easy, and fluent, and his writings were popular. The following is a short specimen of his manner:――
“The analogy, however, of the monuments consulted in geology, and those available in history, extends no further than to one class of historical monuments――those which may be said to be undesignedly commemorative of former events. The canoes, for example, and stone hatchets found in the peat bogs afford an insight into the rude arts and manners of the earliest inhabitants of our island; the buried coin fixes the date of the reign of some Roman emperor; the ancient encampment indicates the districts once occupied by invading armies, and the former method of constructing military defences; the Egyptian mummies throw light on the art of embalming, the rites of sepulture, or the average stature of the human race in ancient Egypt. This class of memorials yields to no other in authenticity, but it constitutes a small part only of the resources on which the historian relies; whereas in geology it forms the only kind of evidence which is at our command. For this reason we must not expect to obtain a full and connected account of any series of events beyond the reach of history. But the testimony of geological monuments, if frequently imperfect, possess at least the advantage of being free from all suspicion of misrepresentation. We may be deceived in the inferences which we draw, in the same manner as we often mistake the nature and import of the phenomena observed in the daily course of nature; but our liability to err is confined to the interpretation, and, if this be correct, our information is certain.”
Sir Roderick Murchison,1 a distinguished geologist, was a native of Ross-shire, and served in the army from 1807 to 1816. He directed his attention chiefly to a series of strata in the district bordering on England and Wales, inhabited in early times by the British tribe of the Silures; and after working four years in classifying the rocks and deposits, he separated them into four formations, and showed that each is characterised by peculiar organic remains: and, in 1835, he divided them into a lower and upper group, both of which he anticipated would be found applicable to wide regions of the earth, and named them the Silurian System, the details of which he published under this title in 1839. In 1854, his later researches were published under the title of _Siluria: the History of the Oldest Known Rocks containing Organic Remains_.
1 Born in 1792; died 1871.
He spent many years in Russia and in other countries in geologic explorations; and, in 1846, he published _The Geology of Russia and the Ural Mountains_, in which he was assisted by Count A. von Keyserling and E. de Verneuil. He is also the author of upwards of one hundred separate memoirs presented to scientific societies. In 1844, after examining some specimens of Australian rocks brought to this country, and comparing them with those of the auriferous Ural Mountains, he came to the conclusion that gold existed in Australia. Two years later, he urged the Cornish tin miners to emigrate to the colony of New South Wales, where they could obtain gold from the alluvial soil in the same way as they extracted tin from the gravel of their own country.
The following is a summary of the Siluria strata as they occur in the district mentioned above, upon which Sir Roderick mainly founded his system; they represent a thickness of about nine thousand feet:――
{ Finely laminated reddish sandstone and shales. { Micaceous grey sandstones of varying thickness. Upper { Argillaceous limestone. strata. { Calcareous shale, with concretions of limestone. { Concretionary limestone and argillaceous shale. { Shelly limestone and sandstone. { Gritty sandstones and shales.
{ Grits and sandy shales. Lower { Thick-bedded white freestone. strata. { Dark-coloured flagstones and slates. { Dark-coloured calcareous flags, bands of limestone, { and gritty flagstones.
Excepting a few indistinct fragments of land plants in the uppermost beds, the whole remains are characteristically marine, and evince conditions favourable to a variety of invertebrate life. Among the prevailing and distinctive fossils are fucoids or seaweed plants, corals, radiate animals, sea-worms, and shell-fish in great variety. And strata characterised by these fossils are largely developed in many countries, especially along the flanks of the older mountain-chains. “They occur in Wales, in Cumberland, in Westmoreland; along the south of Scotland; south-east of Ireland; the south of France, Spain, Scandinavia, Russia, and Bohemia; in Asia Minor; along the Himalaya and Altai ranges; in Australia and New Zealand; along the Andes, Rocky Mountains, and Appalachians in America.”
I have already mentioned Hugh Miller as a geologist, and no one was more ready than Sir Roderick Murchison to recognise his merits and to applaud his genius. Murchison received the honour of knighthood in 1846. The first editor of the _Scotsman_, Mr. Maclaren, was a student of geology, and published an _Account of the Geology of Fife and the Lothians_ in 1839. It was, however, Hugh Miller that made geology popular in Scotland, and gave a great impulse to its study.
SECTION II.
_Progress of Mechanical Science._
The relation between physical science and the mechanical arts are obvious in many ways. The exact boundaries between science and art are as undefinable as those which separate the kingdoms of nature from one another. If there are arts that cannot be called scientific, there are others which have contributed more to the store of knowledge than they ever drew from it, as the progress of science must be gathered from the records of experience, and in order to understand its importance, we must consult many of the varied pages of this record. In the progress of physical and mechanical science, as in that of social science and civilisation, the retarding obstacles everywhere mainly consist in the want or the imperfection of the requisite means――for observation, experiment, and verification in the former, for organisation and just and mutual union in the latter; in both spheres the chief retarding causes are the lack of appropriate and available means at the time and place when they were most needed. Many of the instruments and the apparatus required for observation and experiments in physical science are complicated and expensive, such as telescopes in astronomy, organs in acoustics, and so on, and skill and art are required to construct them; hence it has often happened that imperfect instruments and the want of the necessary apparatus have greatly retarded the progress of physical science. It is, therefore, plain that mechanical art is an indispensable element in the advancement of physical science, and that physical and mechanical science are important factors in the development of civilisation. For the necessities and the requirements of a progressive nation or empire are constantly increasing, and in order to hold its own, it must not only continue to improve and develop its moral and social organisations, but it must also exert itself to the utmost to advance its knowledge, science, and all the practical arts which minister to the life and to the enjoyment of mankind. This is the solemn decree of nature, and nothing else in the universe is available for the human race.
I will indicate briefly what Scotland has done to advance mechanical science and steam power. The order of exposition is determined by the intersective efforts of the chief actors in the early stage of this subject, and these were Mr. Watt, Dr. Black, Dr. Robison, and some other professors in the University of Glasgow. Of the discoveries and experiments of Dr. Black I have already spoken, and of his friendship and scientific relations with Mr. Watt; and it seems necessary now to introduce Dr. Robison,――a Scotsman, who contributed much to spread the knowledge of mechanical science in his native country and throughout the civilised world.
John Robison1 was educated in the University of Glasgow from the twelfth year of his age to the nineteenth, and thus had the advantage of the instruction of those able professors who raised the fame of this ancient University――Adam Smith, Dr. Black, and Dr. Robert Simson.2 From an early period of his life he manifested a strong bent for physical and mechanical science; and it was in his student days that he formed a friendship with Mr. Watt which continued throughout their lives. Their acquaintance began in 1757, and the occasion of it is told by Robison himself thus:――“I was then a student in the University of Glasgow, and studying the science which I now profess to teach. The University was then building an astronomical observatory. Mr. Watt was employed to repair and set up a very noble collection of instruments bequeathed to the University by Mr. Macfarlane of Jamaica, a gentleman well known to the scientific world. Mr. Watt had apartments and a workshop within the College. I had from my earliest youth a great relish for the natural sciences, and particularly for mathematical and mechanical philosophy. I was eager to be acquainted with the practice of astronomical observation, and my wishes were much encouraged by the celebrated Dr. Simson, professor of geometry; Dr. Dick, professor of natural philosophy; and Dr. Moore, professor of Greek――gentlemen eminent for their mathematical abilities. These gentlemen brought me with them into Mr. Watt’s shop; and when he saw me thus patronised, or introduced, his natural complaisance made him readily indulge my curiosity.
1 Born in 1739; died in 1805.
2 Dr. Simson held the chair of mathematics from 1711 to 1761, and at his death he bequeathed to the University his collection of mathematical books, supposed to be the most complete then in the kingdom.――Macgregor’s _History of Glasgow_, page 343.
“After first feasting my eyes with the view of fine instruments, and prying into everything, I conversed with Mr. Watt. I saw a workman, and expected no more; but was surprised to find a philosopher, as young as myself, and always ready to instruct me. I had the vanity to think myself a pretty good proficient in my favourite study, and was rather mortified at finding Mr. Watt so much my superior. But his own high relish for those things made him pleased with the chat of any person who had the same tastes with himself, or his innate complaisance made him indulge my curiosity, and even encourage my endeavours to form a more intimate acquaintance with him. I lounged much about him, and, I doubt not, was frequently teasing him. Thus our acquaintance began.”1
1 _Narrative of Mr. Watt’s Inventions of the Improved Engine_, by Professor Robison.
In 1759, Robison left Glasgow, and went to sea as tutor to a son of Admiral Knowles, with the rank of a midshipman. In this stage of his life he saw some service in Canada; and the information which he acquired by his extended means of observation was afterwards turned to good account. He returned to Glasgow in 1764, and then concentrated his attention on the study of chemistry under Dr. Black; and in 1766, on the removal of Dr. Black to Edinburgh, Robison was appointed professor of chemistry in the University of Glasgow. But in 1770, he again joined Admiral Knowles as his private secretary and accompanied him to Russia; and this led to his appointment as professor of mathematics in the naval school at Cronstadt in 1772. In nine months he learned to speak and write the Russian language with ease, and performed his duties in a manner satisfactory to all concerned. In 1774, he was elected to the chair of natural philosophy in the University of Edinburgh, and was warmly invited to return to Scotland. He accepted the appointment, and spent the remainder of his life in incessant toil and scientific occupation.
His first course of lectures was delivered in Edinburgh, in 1774‒75, and embraced the sciences of mechanics, hydrodynamics, astronomy, optics, electricity, and magnetism, all of which he treated with remarkable clearness and precision. As a lecturer and expositor in his own department, he was among the most eminent of his time in Britain. He was succeeded in the chair by John Playfair, who had previously been for twenty years professor of mathematics in this University; and he is the author of the fine historical Dissertation on the progress of mathematical and physical science, published in one of the supplements of the _Encyclopædia Britannica_, and some other writings connected with science.
Professor Robison’s works consist of――(1) _Elements of Mechanical Philosophy_, of which only the first volume was completed and published in 1804, containing “Dynamics” and “Astronomy;” and (2) upwards of forty separate treatises and articles contributed to the _Encyclopædia Britannica_, which treated on several of the more experimental branches of physical science, and on the following practical branches: (1) the art of music, with which he was himself practically conversant, (2) strength of materials, (3) carpentry, (4) roof, (5) the construction of arches and centres for bridges, (6) watch-work, (7) rivers, (8) waterworks, (9) pumps, (10) variations of the compass, (11) seamanship, (12) machinery, (13) steam, and (14) the steam-engine. As already mentioned, Sir David Brewster edited the above works, along with some selections from the author’s manuscript; and to the articles “Steam” and the “Steam-engine” Mr. Watt, at the request of Brewster, contributed notes and additions.
James Watt was born at Greenock in 1736, and received his education there,1 in the commercial school and grammar school, in which he learned the elements of Latin and Greek, and attained a fair knowledge of mathematical science. To this was added the homely but important tuition which he received from his father, who carried on a business in articles used in navigation, ship fittings, and tackle. “He had a small forge set up for his own use; and was fond of repairing and making all sorts of instruments; he was also at a very early age informed about the use and principles of construction of the telescope, quadrants, and other optical instruments of which his father kept a stock for the supply of ships.” From the aptitude which he showed for this kind of handiwork and in accordance with his own choice, it was decided that he should qualify himself for the trade of a mathematical instrument maker.2
1 His kinsman, James P. Muirhead, published his _Life of Watt_ in 1858, and he had before, in 1854, published _The Origin and Progress of the Mechanical Inventions of James Watt_, in three volumes.
2 Muirhead’s _Life of Watt_, pages 25‒30.
In 1755, Watt proceeded to London with the aim of attaining more skill in the art of instrument making. An agreement was made with Mr. John Morgan, a mathematical instrument maker in Finch Lane, Cornhill, that young Watt should receive one year’s instruction, for which he was to pay in return twenty guineas, and give his labour during that time in the business. As was expected, he made rapid progress. When his year’s working was completed, he announced “that he could now make a brass sector with a French joint, which is reckoned as nice a piece of framing work as is in the trade.”1
1 _Ibid._, pages 36, 37.
He returned to Scotland in the month of August, 1756, and shortly after proceeded to Glasgow with the object of finding employment; and in the month of October, the authorities of the University engaged him to clean and set up the Macfarlane collection of instruments in the College, as already mentioned. Thus it was that Watt was introduced and became so intimate with the professors and the leading men of this University; but he never attended any of Dr. Black’s courses of lectures, nor any other course of lectures in the University. He finished this piece of work before the month of December. He then tried to establish himself in the city of Glasgow; but he met with unforeseen obstacles. As he had not served a regular apprenticeship, and was not the son of a burgess, the rules of the craftsmen came into effect, and he was forbidden to set up a workshop.
But to the credit of the eminent men who then illumined the University of Glasgow, they nobly came to the rescue of the great mechanical genius. And in the summer of 1757, they gave him permission to occupy apartments and open a shop within the College buildings, and to use the title of “Mathematical Instrument Maker to the University.” He continued to occupy his rooms and workshop in the College till 1763, when he quitted them for a small house in the city; but the intimate and friendly relations which he had formed with the professors and others connected with the University were continued throughout his life. Turning attention to his inventions, touching steam itself, he says:――
“It was known very long before my time, that steam was condensed by coming into contact with cold bodies, and that it communicated heat to them.
“It was known by some experiments of Dr. Cullen, and others, that water and other liquids boiled in vacuo at very low heats; water below 100°.
“It was known to some philosophers, that the capacity or equilibrium of heat, as we then called it, was much smaller in mercury and in tin than in water.
“It was also known, that evaporation caused the cooling of the evaporating liquid, and bodies in contact with it.
“I had myself made experiments to determine the following facts:―― 1st, The capacities for heat of iron, copper, and some sorts of wood, comparatively with water. Similar experiments had also subsequently been made by Dr. Irvine, on these and other metals.
“2nd, The bulk of steam was compared with that of water.
“3rd, The quantity of water which could be evaporated in a certain boiler by a pound of coals.
“4th, The elasticities of steam at various temperatures greater than that of boiling water, and an approximation to the law which it followed at other temperatures.
“5th, How much water, in the form of steam, was required every stroke by a small Newcomen’s engine, with a wooden cylinder six inches diameter, and twelve inches long in the stroke.
“6th, I had measured the quantity of cold water required in every stroke to condense the steam in that cylinder, so as to give it a working power of about 7 pound on the inch.” He found that “water converted into steam can heat about six times its own weight of well water.... Being struck with this remarkable fact, and not understanding the reason of it, mentioned it to my friend Dr. Black, who then explained to me his doctrine of latent heat.”1 This was in 1764.
1 Letter and notes by Mr. Watt to Robison’s _Mechanical Philosophy_, Volume II., pages 7, 8, 113‒116.
Touching the steam-engine, Watt says:――“My attention was first directed in the year 1759 to the subject of steam-engines, by the late Dr. Robison himself, then a student in the University of Glasgow, and nearly of my own age. He at that time threw out an idea of applying the power of the steam-engine to the moving of wheel carriages, and other purposes, but the scheme was not matured, and soon after abandoned on his going abroad.”1
1 _Ibid._, Volume II., page 113.
Watt’s first improvement on the steam-engine was made in 1765; and it consisted of the idea of introducing a separate condenser for the steam――a contrivance to prevent the cooling of the cylinder, and make the vacuum more perfect by condensing the steam in a vessel distinct from the cylinder. This was patented in the beginning of the year 1769, and in his specification he undertakes to lessen the consumption of steam and fuel in steam engines. This patent was renewed for a period of twenty-five years by an Act of Parliament in 1775. He took out another patent, in 1781, “for certain new methods of applying a continuous circular motion round an axis, and thereby give motion to the wheels of mills or other machines.” The specification contains a description of five different modes of rotative motions. In 1782, he took out another patent, and the specification in this one contains six contrivances for equalising steam-power on the expansive principle; and among these, the double-acting engine, in which the steam is alternately applied to press on each side of the piston, while a vacuum is formed on the other side.
One of the most important of his improvements of the steam-engine was inserted in his patent of ♦1784. This is the “parallel motion,” which he described thus:――“Methods of causing the piston-rods, pump-rods, and other parts of the engine, to move in perpendicular or other straight lines, and to enable the engine to act upon the working beams both in pushing and in pulling; and three varieties are described.” This specification also described improved modes of applying the steam-engine to drive mills which have many wheels requiring to move round in concert; a simple method of applying the power of the steam-engine to the working of heavy hammers or stampers; a portable steam-engine and machinery for moving wheeled carriages.1
♦ “1874” replaced with “1784”
1 Watt’s Notes to Robison’s _Mechanical Philosophy_, Volume II., pages 118‒121, 149‒151; also Muirhead’s _Life of Watt_, pages 180, 247, 278‒284, 285, 293‒296.
It was only after great perseverance, patience, hard toil, and thought, and many disappointments and untold anxieties that Mr. Watt at last attained success. It was fortunate for him, and for mankind, that from his first appearance in Glasgow he won not a few warm and able friends――men who knew and appreciated his great genius and the worth of his character, encouraged him, and stood by his side in one of the greatest trials of his life, to give their testimony to his rare genius and unimpeachable integrity.1
1 With regard to two of the gentlemen alluded to above, I will quote Mr. Watt’s own words:――“Although Dr. Black’s theory of latent heat did not suggest my improvements on the steam-engine, yet the knowledge upon various subjects which he was pleased to communicate to me, and the correct modes of reasoning and of making experiments of which he set me the example, certainly conduced very much to facilitate the progress of my inventions; and I still remember with respect and gratitude the notice he was pleased to take of me when I very little merited it, and which continued throughout his life.
“To Dr. Robison I am also bound to acknowledge my obligations for very much information and occasional assistance in my pursuits, and above all for his friendship, which ended only with his life; a friendship which induced him, when I was beset with a host of foes, to come to London in the depth of winter, and appear as a witness for me in a court of justice, whilst labouring under an excessively painful disorder, which ultimately deprived him of life. To the remembrance of that friendship is principally owing my taking upon myself the office of his commentator at my advanced age.”――Letter of Mr. Watt, in Robison’s _Mechanical Philosophy_, Volume II., page 9.
Watt entered into partnership with Mr. Boulton, of Birmingham, and, after 1775, for many years he resided in that city; and continued his exertions, with little intermission, to the further improvement of the steam engines. The business proved successful, and Watt retired at the end of the last century, leaving two of his sons in the establishment, which continued to prosper. The ingenious improver of the steam-engine, after many efforts and struggles, was enabled to spend the evening of his days in comparative wealth and leisure.
Mr. Watt invented many things beside his improvements of the steam-engine, amongst which may be mentioned a micrometer for measuring distances, which he used in his surveys of the Crinan and Gilp, and the Tarbert intended canals, and in other surveys of canals which he was employed to make; also, a copying-machine, which was patented in 1780, described as a “new method of copying letters and other writings expeditiously.” At an early period of his career he built some organs. He planned and superintended the construction of the Monkland canal.
He wrote comparatively little, but he was an exceedingly well-informed man. He was fond of chemistry as well as mechanics, and was well versed in the theory and practice of both. He discovered the composition of water, and his friends have maintained his priority to Cavendish in this discovery. He was elected a Fellow of the Royal Society of Edinburgh in ♦1784; of the Royal Society of London in 1785, and a correspondent member of the Institute of France in 1808. In 1806, the University of Glasgow conferred on him the honorary degree of LL.D.; and in 1814, the Academy of Sciences of the Institute of France elected him one of its eight foreign Associates. After the toils and heat of the day, his evening closed in calm serenity; full of honour and of years, beloved by his friends, and surrounded by his family, he passed away on the 25th of August, 1819, at Heathfield, near Birmingham, in the eighty-third year of his age. Statesmen, philosophers, men of science, and men of the world united in extolling the worth of his character and the greatness of his genius. From the notices of his death, I shall quote a part of the one which Lord Jeffrey wrote:――
♦ “1748” replaced with “1784”
“We have said that Mr. Watt was the great improver of the steam-engine; but, in truth, as to all that is admirable in its structure, or vast in its utility, he should rather be described as its inventor. It was by his inventions that its action was so regulated as to make it capable of being applied to the finest and most delicate manufactures, and its power so increased as to set weight and solidity at defiance. By his admirable contrivance, it has become a thing stupendous alike for its force and its flexibility――for the prodigious power which it can exert, and the ease, and precision, and ductility, with which it can be varied, distributed, and applied.... It can engrave a seal, and crush masses of obdurate metal before it――draw out without breaking a thread as fine as gossamer, and lift a ship of war like a bauble in the air. It can embroider muslin and forge anchors, cut steel into ribbons, and impel loaded vessels against the fury of the winds and waves.
“It would be difficult to estimate the value of the benefits which these inventions have conferred upon this country. There is no branch of industry that has not been indebted to them; and, in all the most material, they have not only widened most magnificently the field of its exertions, but multiplied a thousand-fold the amount of its productions.... It has increased indefinitely the mass of human comforts and enjoyments, and rendered cheap and accessible, all over the world, the materials of wealth and prosperity. It has armed the feeble arm of man, in short, with a power to which no limits can be assigned; completed the dominion of mind over the most refractory qualities of matter; and laid a sure foundation for those future miracles of mechanic power which are to aid and reward the labours of after generations. It is to the genius of one man, too, that all this is mainly owing, and certainly no man ever bestowed such a gift on his kind. The blessing is not only universal, but unbounded; and the fabled inventors of the plough and the loom, who were deified by the erring gratitude of their rude contemporaries, conferred less important benefits on mankind than the inventor of our present steam-engine.
“This will be the fame of Watt with future generations; and it is sufficient for his race and his country. But to those to whom he more immediately belonged, who lived in his society and enjoyed his conversation, it is not, perhaps, the character in which he will be most frequently recalled, most deeply lamented, or even most highly admired. Independently of his great attainments in mechanics, Mr. Watt was an extraordinary, and in many respects a wonderful man. Perhaps no individual in his age possessed so much and such varied and exact information――had read so much, or remembered what he had read so accurately and well. He had infinite quickness of apprehension, a prodigious memory, and a certain rectifying and methodising power of understanding, which extracted something precious out of all that was present to it. His stores of miscellaneous knowledge was immense――and yet less astonishing than the command he had at all times over them. It seemed as if every subject that was casually started in conversation with him, had been that which he had been last occupied in studying and exhausting; such was the copiousness, the precision, and the admirable clearness of the information which he poured out upon it without effort or hesitation. Nor was this promptitude and compass of knowledge confined in any degree to the studies connected with his ordinary pursuits. That he should have been minutely and extensively skilled in chemistry and the arts, and in most of the branches of physical science, might perhaps have been conjectured; but it could not have been inferred from his usual occupations, and probably is not generally known that he was curiously learned in many branches of antiquity, metaphysics, medicine, and etymology, and perfectly at home in all the details of architecture, music, and law. He was well acquainted, too, with most of the modern languages, and familiar with their most recent literature. Nor was it at all extraordinary to hear the great mechanician and engineer detailing and expounding, for hours together the metaphysical theories of the German logicians, or criticising the measures or the matter of the German poetry.
“It is needless to say, that, with those vast resources, his conversation was at all times rich and instructive in no ordinary degree: but it was, if possible, still more pleasing than wise, and had all the charms of familiarity, with all the substantial treasures of knowledge. No man could be more social in his spirit, less assuming or fastidious in his manners, or more kind and indulgent towards all who approached him.... He had a certain quiet and grave humour, which ran through most of his conversation, and in a vein of temperate jocularity, which gave infinite jest and effect to the condensed and inexhaustible information which formed its main staple and characteristic.
“In his temper and disposition he was not only kind and affectionate, but generous, and considerate of the feelings of all around him; and gave the most liberal assistance and encouragement to all young persons who showed any indications of talent, or applied to him for patronage or advice.... All men of learning and science were his cordial friends; and such was the influence of his mild character and perfect fairness and liberality, even upon the pretenders to these accomplishments, that he lived to disarm even envy itself, and died, we verily believe, without a single enemy.”
The application of steam power to navigation in the end of the last century, and to railway trains in the present, has produced the most striking results; and although Watt was not directly connected himself with the early attempts of steam navigation, still its introduction was greatly dependent on his improvements of the steam-engine. The development of steam-power in manufactories and other forms will be afterwards noticed; but before quitting the subject, I will describe the earliest attempts to propel ships by steam. Many projects were spoken of which were never realised. But Mr. Miller of Dalswinton, assisted by Mr. James Taylor, tutor in his family, formed a plan for vessels with paddle wheels to be driven by a steam-engine; and with the assistance of Mr. Symington of Wanlockhead, a practical engineer, a small engine and a boat were constructed and fitted up: and in October, 1788, this boat was launched on the Loch of Dalswinton, in Dumfriesshire, and she attained a speed of five miles an hour. They then built a larger boat, the engine of which Mr. Symington constructed at Carron ironworks; and, in 1789, this vessel was launched on the Forth and Clyde Canal and propelled by steam, and she attained a speed of about seven miles an hour. These are among the earliest attempts of steam navigation of which we have authentic record. For some time after, this new enterprise lingered; but in the very beginning of the present century Mr. Symington’s experiment was repeated on the Thames with complete success. While in America on the river Hudson, Mr. Robert Fulton, the son of a Scotsman who emigrated from Dumfriesshire, started a steamboat with an engine of Boulton and Watt, in 1807. It is a curious fact that, in the year 1814, Scotland had five steam vessels, while England had not a single one. In the following year, however, England had three, and in 1820, she had seventeen; while Scotland had fourteen. Subsequently, owing to causes easily understood, steam ships increased in number far more rapidly in England than in Scotland, though not faster in proportion to the population and wealth of the latter country.
The most striking and important of the improvements in steam vessels which have been made in the present century is the substitution of the screw-propeller for the paddle-wheels; while in the construction of ships themselves wood has been superseded by iron and steel.
With regard to the importance, the variety, the subtilty, and the power of its practical applications, and the latent or as yet undeveloped power inherent in it, the science of electricity takes a high rank; and with a brief and consequently a very imperfect notice of it in these various relations, this chapter will conclude.
The science of electricity is of modern growth; very little was known of its nature or powers prior to the last century, though some of its phenomena attracted the attention of a few scientific men in the seventeenth century. Between the years 1720 and 1736, Stephen Grey, assisted by Wheeler, discovered that the human body conducts electricity, that it acts at a distance――motion in light bodies being produced by frictional electricity at a distance of 666 feet; he also stated the fact of electric induction and other phenomena. About 1733, Dufay originated his dual theory of two electric fluids; and stated that two bodies similarly electrified repel each other, and attract bodies oppositely electrified. What was termed the Leyden Jar was discovered by several persons in 1745; and the following year Winckler constructed the Leyden Battery. About the same time, important researches were made by Watson, Canton, and others. In 1747, Franklin enounced his theory of a single fluid; he termed the vitreous electricity positive, and the resinous negative; and, in 1752, he demonstrated the identity of the electric spark and lightning, drawing electricity from a cloud by the use of a kite. Still this subtle and powerful element was then but little understood; and, in 1752, Professor Richmann was killed at St. Petersburg while repeating Franklin’s experiments. Since this period the subject has been treated continuously by many able and famous men of science.
The term electricity, as now applied, includes various phenomena of very different characters; such as magnetism, frictional electricity, and voltaic electricity. Two general properties may be noted――(1) polarity and (2) current action. In the first there is a uniformity through all its modes, and it is the pervading attribute which gives a distinctive character to all the phenomena: the second peculiarity of the electric forces is that they can be carried to any distance through solid conductors, so as to discharge themselves at any point. Frictional electricity is generated by mechanical force in electrical machines.
The practical applications of the electric forces are now numerous, and all of comparatively recent introduction. Although the idea of applying electricity to communicate signals was conceived by Watson about the middle of the last century, the earliest proposal of this appeared in the _Scots Magazine_ for February, 1753, when a correspondent from Renfrew, who signed himself C. M., proposed several kinds of telegraphs, acting by the attractive force of electricity, conveyed by a series of parallel wires equal in numbers to the letters of the alphabet, and insulated by supports of glass or jeweller’s cement at every twenty yards. Words were to be spelt by the electricity attracting letters, or by striking bells corresponding to letters. Towards the latter part of the last century and the early part of this various plans of telegraphs were proposed by different men; but 1837 is the date of the practical realisation of the electric telegraph. A few years later it began to be employed in connection with the working of railways; and it is obvious that the railway system could not have been developed without the aid of the electric telegraph, or some similar method of rapid and instantaneous signalling. The modes of electric telegraph have been much perfected, and the systems of communication immensely developed, within recent years.
Among those who have advanced the knowledge of electricity and the development of its practical application during the past half century, the veteran Professor of Natural Philosophy in the University of Glasgow, Lord Kelvin, holds a distinguished place. He has made many experiments, practical applications, and written much on the subject.
Submarine electric telegraphs were successfully introduced in 1851, when the first line between Dover and Calais was opened; and it has since been greatly developed, and direct telegraphic communication established between Europe and America many years ago. Electric clocks were introduced in 1854, and are now common.
An apparatus for regulating the electric light was first devised and exhibited by Staite and Petrie in 1848. Jules Duboscq’s electric lamp was shown at the Paris exhibition in 1855; and, in 1856, it was employed by Professor Tyndall for illustrating his lectures on light and colour, which he delivered that year at the Royal Institution in London. Since, the electric light has been greatly developed, and used for lighting public buildings, places of business, and the streets of cities; and if the cost of its production was reduced it would be more universally used for lighting purposes.
In 1854, M. Bonelli, of Turin, invented a plan of employing magnets and electro-magnets in weaving, by which he proposed to supersede the tedious and costly Jacquard system of cards. His loom was set up in London in 1859; and, in the summer of 1860, Professor Faraday lectured upon it at the Royal Institution. There are other applications of electricity which it is unnecessary to enumerate.
An exceedingly useful and beautiful application has recently been made in the science of acoustics, by the invention of the telephone, which transmits the sounds of spoken language along wires to a considerable distance.
In concluding this chapter, the importance of mathematical science was indicated, and the Scotch mathematicians noticed; Dr. Black’s researches and discovery of latent heat, and Leslie’s treatment of radiant heat and experiments were explained; I then indicated the results of more recent researches and referred to spectrum analysis. The writings, experiments, observations, and the discoveries of Sir David Brewster were noticed; and the contributions of several Scotsmen to geology were noted. The department of mechanical or applied science was then treated, and the writings of Dr. Robison and his teaching in this relation were noticed, and the bearing of the discovery of latent heat on the application of steam-power. A short account of Watt’s career was given; his experiments on steam, improvements on the steam-engine, his struggles, and ultimate success, his genius, accomplishments, and character, were noticed. The early attempts of steam navigation were explained; and finally some account was presented of the discovery and the varied applications of electricity.