Popular Science Monthly/Volume 7/October 1875/Sketch of Professor Stokes
|←Animal Life in Madagascar||Popular Science Monthly Volume 7 October 1875 (1875)
Sketch of Professor Stokes
|Correspondence and Editor's Table→|
THE subject of this notice, George Gabriel Stokes, was born August 13, 1819, at Skreen, in the county of Sligo, Ireland, his father being rector of the parish. At an early age he was sent to a school at Dublin, conducted by the Rev. R. H. Wall, D.D. Here he remained for about three years, when he entered a college at Bristol, as a preparation for the university. After two years spent at Bristol, young Stokes, in 1837, entered Pembroke College, University of Cambridge, and four years later graduated Bachelor of Arts, at the same time winning the highest honors of the university—the Senior Wranglership and the First Smith's Prize. In the same year he was elected to a fellowship in his college. In 1849 he was appointed to the Lucasian chair of Mathematics in the university, and thus became the successor of Newton. Mr. Stokes enjoyed the emoluments of his fellowship until 1857, when he vacated that position by taking a wife. Later, by an amendment of the statutes of Pembroke, he was reinstated in his fellowship. In 1851 he was chosen Fellow of the Royal Society, and in the following year received the Rumford medal "in recognition of his services to the cause of science by the discovery of the change of the refrangibility of light." The "Philosophical Transactions" for 1852 gives an account of this discovery. In 1854 Mr. Stokes was elected one of the secretaries of the Royal Society. He was President of the British Association for the Advancement of Science at the Exeter meeting, 1869. In 1871 the University of Edinburgh conferred upon Prof. Stokes the degree of Doctor of Laws.
It requires merit of no common order to enable a man to attain the high honor of occupying the chair of Newton, at the early age of thirty. Mr. Stokes's election to the Lucasian professorship was a surprise to the undergraduates of Cambridge, who had expected to see the place filled by some man of European fame. But the wisdom of the choice was soon made manifest, and the students of Cambridge recognized in the new professor not only an exceptionally able and learned man, but also one whose whole heart and soul were devoted to the advancement of his pupils. How Prof. Stokes won the confidence and love of the students is told by Prof. P. G. Tait, who at the time was himself an undergraduate at Cambridge. In a memoir recently published in Nature, Prof. Tait writes that, a few months after his election to the chair of Mathematics, Prof. Stokes gave public notice that he considered it part of the duties of his office to assist any member of the university in difficulties that lie might encounter in his mathematical studies. Here was, thought the students, "a single knight fighting against the whole mêlée of the tournament." But they soon discovered their mistake, and felt that the undertaking was the effect of an earnest sense of duty on the conscience of a singularly modest but profoundly learned man.
As a mathematician and physicist, Stokes stands in the foremost rank, whether of his contemporaries or of his predecessors. "Newton's wonderful combination of mathematical power with experimental skill." writes Prof. Tait, "without which the natural philosopher is but a fragment of what he should be, lives again in his successor. Stokes has attacked many questions of the gravest order of difficulty in pure mathematics, and has carried out delicate and complex experimental researches of the highest originality, alike with splendid success. But several of his greatest triumphs have been won in fields where progress demands that these distinct and rarely associated powers be brought simultaneously into action. For there the mathematician has not merely to save the experimenter from the fruitless labor of pushing his inquiries in directions where he can be sure that (by the processes employed) nothing new is to be learned; he has also to guide him to the exact place at which new knowledge is felt to be both-necessary and attainable. It is on this account that few men have ever had so small a percentage of barren work, whether mathematical or experimental, as Stokes."
A partial list of Stokes's contributions to science is given in Prof. Tait's memoir. It is there stated that up to 1864 Stokes had published the results of some seventy distinct investigations. Since that year he has published but little, though it is well known that he has in retentis several optical and other papers of the very highest order, which he cannot bring himself to publish in an incomplete form. Many of the papers which have been published by Prof. Stokes are of so rigidly mathematical a character that their titles would fail to convey any idea to the non-mathematical mind. To this category belong the papers entitled "Critical Values of the Sums of Periodic Changes " and "Numerical Calculation of Definite Integrals and Infinite Series." The following incomplete list will serve to show the comprehensiveness of Prof. Stokes's researches in applied mathematics:
"On the Friction of Fluids in Motion, and the Equilibrium and Motion of Elastic Solids," 1845; "Effects of the Internal Friction of Fluids on the Motion of Pendulums," 1850.
Of Stokes's papers stating the results of his researches on the "Undulatory Theory of Light," three are cited by Prof. Tait, viz.: "Dynamical Theory of Diffraction," 1849; "On the Colors of Thick Plates," 1851; "On the Formation of the Central Spot of Newton's Rings beyond the Critical Angle," 1848.
The "Report on Double Refraction," in the "British Association Reports for 1862," was drawn up by Prof. Stokes.
"On the Variation of Gravity at the Surface of the Earth," 1849.
"On the Change of the Refrangibility of Light," 1852. This paper contains his famous experimental explanation of fluorescence, which earned for its author his fellowship in the Royal Society.
Among the papers published by Stokes since the year 1864, two are specially worthy of mention, viz.: "On the Long Spectrum of Electric Light," and "On the Absorption Spectrum of Blood."
In conjunction with the late Mr. Vernon Harcourt, Stokes made a highly-valuable experimental inquiry into what is called Irrationality of Dispersion, chiefly with a view to the improvement of achromatic telescopes.
"There can be no doubt," writes Prof. Tait, "as was well shown by Sir W. Thomson in his presidential Address to the British Association at Edinburgh in 1871, that Stokes (at least as early as 1852) had fully apprehended the physical basis of spectrum analysis, and had pointed out how it should be applied to the detection of the constituents of the atmospheres of the suns and stars. Balfour Stewart's experiments and reasoning date from 1858 only, and those of Kirchhoff from 1859."
Prof. Stokes, however, gives due credit to Kirchhoff. Thus, in his Presidential Address to the British Association, in speaking of the applications of the spectroscope, he says:
To the Editor of the Popular Science Monthly:
IN a paper in The Popular Science Monthly for August, entitled "The Form of Lightning-Rods," Prof. Phin describes an experiment intended to demonstrate the proposition that electricity of high tension travels through the substance of a conductor independently of its superficies.
Without questioning the general truth of this proposition, I would call attention to one or two flaws in the author's demonstration.
He cites the fact that a moderate charge shatters a strip of gold-leaf, while a stronger one fails to affect a wire having less surface and a greater section. From this he deduces his theorem.
This experiment seems to me unsatisfactory, for the reason that a disruptive force may be supposed to be exerted in both cases, but that the superior strength of the wire enables it to resist what destroys the frail gold-leaf. Of course, the same argument will hold if the effect be ascribed mainly to heat, since but little, comparatively, would suffice to fuse the gold-leaf or even to dissipate it as gas.
Prof. Phin, referring to this experiment, says: "Here we see that, while the electricity was at rest [static), the gold-leaf was quite capable of receiving as heavy a charge as the most powerful machine could impart."
It doubtless was "capable of receiving the most powerful charge," but the fact is not proved by the experiment, for, in the position in which the gold-leaf was placed, viz., on the knob of the jar, it was not charged at all!
The charge must have been collected upon the inner coating, through the attraction exercised by the electricity induced upon the exterior. The gold-leaf, in connection with the inside of the jar, was then, properly speaking, no more charged than were objects connected with the outside, e. g., the table, and, to a certain extent, every other object on the surface of the planet.
|L. H. Andrews.|
|Springfield, Mass., August 17, 1875.|
To the above Prof. Phin replies as follows:
"1. The first objection is to the experiment in which a gold wire is shown to be capable of carrying off a discharge which destroys a strip of gold-leaf presenting a far greater surface. Whether we attribute the destroying power to heat or to mechanical force, it is a fact that the thin gold-leaf is destroyed while the stouter wire remains uninjured, and this is all that is necessary to be known so far as lightning-rods are concerned.
"2. The second objection is, that the gold-leaf in contact with the knob of the jar is not 'charged.' Of course, if the gold-leaf is not charged, the same remark applies to the knob itself; how, then, does it happen that, under such circumstances, the knob will powerfully attract or repel (according to circumstances) a pith-ball brought near it? Probably the most intense charge of static electricity could be imparted directly from the prime conductor. This we have often done, without injuring the most delicate strip of gold-leaf, though the passage of a spark, even without the aid of a Leyden jar, will destroy a strip three-eighths of an inch wide."