Part 10 (2/2)

The crystalline lens was the only resource left whereby the accommodation could be effected. The accommodation is, in fact, brought about by the action of the ciliary muscle. The natural form of the lens is more convex than is consistent with distinct vision, except for very near objects. The tension of the suspensory ligament, which is attached to the front of the lens all round its edge, renders the anterior surface of the lens much less curved than it would naturally be. The ciliary muscle is a ring of muscular fibre attached to the ciliary process close to the circ.u.mference of the suspensory ligament. By its contraction it forms a smaller ring, and, diminis.h.i.+ng the external diameter, it releases the tension of the suspensory ligament, thus allowing the crystalline lens to bulge out and adapt itself for the diverging rays coming from near objects. It is the exertion of contracting the ciliary muscle that const.i.tutes the effort of which we are conscious when looking at very near objects. It was not, however, till long after the time of Dr. Young that this complicated action was fully made out, though the change of form of the anterior surface of the crystalline lens was discovered by the change in the image of a bright object formed by reflection.

In the spring of 1794 Young took a holiday tour in Cornwall, with Hudson Gurney, visiting on his way the Duke of Richmond, who was drinking the waters at Bath, under the advice of Dr. Brocklesby. In Cornwall, the mining machinery attracted his attention very much more than the natural beauties of the country. Towards the end of the summer he visited the Duke of Richmond at Goodwood, when the duke offered him the appointment of private secretary. He resolved, however, to continue his medical course, one of the reasons which he alleged being his regard for the Society of Friends, whose principles he considered inconsistent with the appointment of Private Secretary to the Master-General of the Ordnance.

The following winter he spent as a medical student at Edinburgh. Here he gave up the costume of the Society of Friends, and in many ways departed from their rules of conduct. He mingled freely with the university, attended the theatre, took lessons in dancing and playing the flute, and generally cultivated the habits of what is technically known as ”society.” Throughout this change in his life he retained his high moral principles as a guide of conduct, and appears to have acted from a firm conviction of what was right. At the same time, it must be admitted that the breaking down of barriers, however conventional they may be, is an operation attended in most cases by not a little danger.

With Young, the progress of his scientific education may have been delayed on account of the new demands on his time; but besides the study of German, Spanish, and Italian, he appears to have read a considerable amount of general literature during his winter session in Edinburgh. The following summer he took a tour on horseback through the Highlands, taking with him his flute, drawing materials, spirits for preserving insects, boards for drying plants, paper and twine for packing up minerals, and a thermometer; but the geological hammer does not then appear to have been regarded as an essential to the equipment of a philosopher. At Aberdeen he stayed for three days, and reported thus on the university:--

Some of the professors are capable of raising a university to celebrity, especially Copeland and Ogilvie; but the division and proximity of the two universities (King's College and Marischal College) is not favourable to the advancement of learning; besides, the lectures are all, or mostly, given at the same hour, and the same professor continues to instruct a cla.s.s for four years in the different branches. Were the colleges united, and the internal regulations of the system new modelled, the cheapness of the place, the number of small bursaries for poor or distinguished students, and the merit of the instructors, might make this university a very respectable seminary in some branches of science. The fee to a professor for a five-months'

session is only a guinea and a half. I was delighted with the inspection of the rich store of mathematical and philosophical apparatus belonging to Professor Copeland of Marischal College, made in his own house, and partly with his own hands, finished with no less care than elegance; and tending to ill.u.s.trate every branch of physics in the course of his lectures, which must be equally entertaining and instructive.

Before leaving the Highlands, Young visited Gordon Castle, where he stayed two days; and appears to have distinguished himself by the powers of endurance he exhibited in dancing reels. On leaving he writes: ”I could almost have wished to break or dislocate a limb by chance, that I might be detained against my will; I do not recollect that I have ever pa.s.sed my time more agreeably, or with a party that I thought more congenial to my own dispositions: and what would hardly be credited by many grave reasoners on life and manners, that a person who had spent the whole of his earlier years a recluse from the gay world, and a total stranger to all that was pa.s.sing in the higher ranks of society, should feel himself more at home and more at ease in the most magnificent palace in the country than in the humblest dwelling with those whose birth was most similar to his own. Without enlarging on the duke's good sense and sincerity, the d.u.c.h.ess's spirit and powers of conversation, Lady Madeline's liveliness and affability, Louisa's beauty and sweetness, Georgiana's _navete_ and quickness of parts, young Sandy's good nature, I may say that I was truly sorry to part with every one of them.”

Young seems not to have known at this time that it is an essential feature of true gentlefolk to dissipate all sense of constraint or uneasiness from those with whom they are brought into contact and that in this they can be readily distinguished from those who have wealth without breeding. The d.u.c.h.ess of Gordon gave Young an introduction to the Duke of Argyll, so, while travelling through the Western Highlands, he paid a visit to Inverary Castle, and ”galloped over” the country with the duke's daughters. Speaking of these ladies, he says, ”Lady Charlotte ... is to Lady Augusta what Venus is to Minerva; I suppose she wishes for no more. Both are G.o.ddesses.”

On his return to the West of England, he visited the Coalbrook Dale Iron Works, when Mr. Reynolds told him ”that before the war he had agreed with a man to make a flute a hundred and fifty feet long, and two and a half in diameter, to be blown by a steam-engine and played on by barrels.”

On the 7th of the following October Young left London, and after spending six days on the voyage from Yarmouth to Hamburg, he reached Gottingen on the 27th of the same month; two days afterwards he matriculated, and on November 3 he commenced his studies as a member of the university. He continued to take lessons in drawing, dancing, riding, and music, and commenced learning the clavichord. The English students at Gottingen, in order to advance their German conversation, arranged to pay a fine whenever they spoke in English in one another's company. On Sundays it was usual for the professors to give entertainments to the students, though they seldom invited them to dinner or supper. ”Indeed, they could not well afford, out of a fee of a louis or two, to give large entertainments; but the absence of the hospitality which prevails rather more in Britain, is compensated by the light in which the students are regarded; they are not the less, but perhaps the more, respected for being students, and indeed, they behave in general like gentlemen, much more so than in some other German universities.”

At Gottingen Young attended, in addition to his medical lectures, Spithler's lectures on the History and Const.i.tution of the European States, Heyne on the History of the Ancient Arts, and Lichtenberg's course on Physics. Speaking of Blumenbach's lectures on Natural History, Young says, ”He showed us yesterday a laborious treatise, with elegant plates, published in the beginning of this century at Wurzburg, which is a most singular specimen of credulity in affairs of natural history. Dr. Behringen used to torment the young men of a large school by obliging them to go out with him collecting petrifactions; and the young rogues, in revenge, spent a whole winter in counterfeiting specimens, which they buried in a hill which the good man meant to explore, and imposed them upon him for most wonderful _lusus naturae_. It is interesting in a metaphysical point of view to observe how the mind attempts to accommodate itself; in one case, where the boys had made the figure of a plant thick and clumsy, the doctor remarks the difference, and says that Nature seems to have restored to the plant in thickness that which she had taken away from its other dimensions.”

On April 30, 1796, Young pa.s.sed the examination for his medical degree at Gottingen. The examination appears to have been entirely oral. It lasted between four and five hours. There were four examiners seated round a table provided ”with cakes, sweetmeats, and wine, which helped to pa.s.s the time agreeably.” They ”were not very severe in exacting accurate answers.” The subject he selected for his public discussion was the human voice, and he constructed a universal alphabet consisting of forty-seven letters, of which, however, very little is known. This study of sound laid the foundation, according to his own account, of his subsequent researches in the undulatory theory of light.

The autumn of 1796 Young spent in travelling in Germany; in the following February he returned to England, and was admitted a fellow-commoner of Emmanuel College, Cambridge. It is said that the Master, in introducing Young to the Tutors and other Fellows, said, ”I have brought you a pupil qualified to read lectures to his tutors.”

Young's opinion of Cambridge, as compared with German universities, was favourable to the former; but as he had complained of the want of hospitality at Gottingen, so in Cambridge he complained of the want of social intercourse between the senior members of the university and persons _in statu pupillari_. At that time there was no system of medical education in the university, and the statutes required that six years should elapse between the admission of a medical student and his taking the degree of M.B. Young appears to have attracted comparatively little attention as an undergraduate in college. He did not care to a.s.sociate with other undergraduates, and had little opportunity of intercourse with the senior members of the university.

He was still keeping terms at Cambridge when his uncle, Dr.

Brocklesby, died. To Young he left the house in Norfolk Street, Park Lane, with the furniture, books, pictures, and prints, and about 10,000. In the summer of 1798 a slight accident at Cambridge compelled Young to keep to his rooms, and being thus forcibly deprived of his usual round of social intercourse, he returned to his favourite studies in physics. The most important result of this study was the establishment of the principle of interference in sound, which afforded the explanation of the phenomenon of ”beats” in music, and which afterwards led up to the discovery of the interference of light--a discovery which Sir John Herschel characterized as ”the key to all the more abstruse and puzzling properties of light, and which would alone have sufficed to place its author in the highest rank of scientific immortality, even were his other almost innumerable claims to such a distinction disregarded.”

The principle of interference is briefly this: When two waves meet each other, it may happen that their crests coincide; in this case a wave will be formed equal in height (amplitude) to the sum of the heights of the two. At another point the crest of one wave may coincide with the hollow of another, and, as the waves pa.s.s, the height of the wave at this point will be the difference of the two heights, and if the waves are equal the point will remain stationary.

If a rope be hung from the ceiling of a lofty room, and the lower end receive a jerk from the hand, a wave will travel up the rope, be reflected and reversed at the ceiling, and then descend. If another wave be then sent up, the two will meet, and their pa.s.sing can be observed. It will then be seen that, if the waves are exactly equal, the point at which they meet will remain at rest during the whole time of transit. If a number of waves in succession be sent up the string, the motions of the hand being properly timed, the string will appear to be divided into a number of vibrating segments separated by stationary points, or nodes. These nodes are simply the points which remain at rest on account of the upward series of waves crossing the series which have been reflected at the top and are travelling downwards. The division of a vibrating string into nodes thus affords a simple example of the principle of interference. When a tuning-fork is vibrating there are certain hyperbolic lines along which the disturbance caused by one p.r.o.ng is exactly neutralized by that due to the other p.r.o.ng. If a large tuning-fork be struck and then held near the ear and slowly turned round, the positions of comparative silence will be readily perceived. If two notes are being sounded side by side, one consisting of two hundred vibrations per second and the other of two hundred and two, then, at any distant point, it is clear that the two sets of waves will arrive in the same condition, or ”phase,” twice in each second, and twice they will be in opposite conditions, and, if of the same intensity, will exactly destroy one another's effects, thus producing silence. Hence twice in the second there will be silence and twice there will be sound, the waves of which have double the amplitude due to either source, and hence the sound will have four times the intensity of either note by itself.

Thus there will be two ”beats” per second due to interference. Later on this principle was applied by Young to very many optical phenomena of which it afforded a complete explanation.

Young completed his last term of residence at Cambridge in December, 1799, and in the early part of 1800 he commenced practice as a physician at 48, Welbeck Street. In the following year he accepted the chair of Natural Philosophy in the Royal Inst.i.tution, which had shortly before been founded, and soon afterwards, in conjunction with Davy, the Professor of Chemistry, he undertook the editing of the journals of the inst.i.tution. This circ.u.mstance has already been alluded to in connection with Count Rumford, the founder of the inst.i.tution. He lectured at the Royal Inst.i.tution for two years only, when he resigned the chair in deference to the popular belief that a physician should give his attention wholly to his professional practice, whether he has any or not. This fear lest a scientific reputation should interfere with his success as a physician haunted him for many years, and sometimes prevented his undertaking scientific work, while at other times it led him to publish anonymously the results he obtained. This anonymous publication of scientific papers caused him great trouble afterwards in order to establish his claim to his own discoveries. Many of the articles which he contributed to the supplement to the fourth, fifth, and sixth editions of the ”Encyclopaedia Britannica” were anonymous, although the honorarium he received for this work was increased by 25 per cent. when he would allow his name to appear. The practical withdrawal of Young from the scientific world during sixteen years was a great loss to the progress of natural philosophy, while the absence of that suavity of manner when dealing with patients which is so essential to the success of a physician, prevented him from acquiring a valuable private practice.

In fact, Young was too much of a philosopher in his behaviour to succeed as a physician; he thought too deeply before giving his opinion on a diagnosis, instead of appearing to know all about the subject before he commenced his examination, and this habit, which is essential to the philosopher, does not inspire confidence in the pract.i.tioner. His fondness for society rendered him unwilling to live within the means which his uncle had left him, supplemented by what his scientific work might bring, and it was not until his income had been considerably increased by an appointment under the Admiralty that he was willing to forego the possible increase of practice which might accrue by appearing to devote his whole attention to the subject of medicine. It was this fear of public opinion which caused him, in 1812, to decline the offer of the appointment of Secretary to the Royal Society, of which, in 1802, he accepted the office of Foreign Secretary.

Young's resignation of the chair of Natural Philosophy was, however, not a great loss to the Royal Inst.i.tution; for the lecture audience there was essentially of a popular character, and Young cannot be considered to have been successful as a popular lecturer. His own early education had been too much derived from private reading for him to have become acquainted with the difficulties experienced by beginners of only average ability, and his lectures, while most valuable to those who already possessed a fair knowledge of the subjects, were ill adapted to the requirements of an unscientific audience. A syllabus of his course of lectures was published by Young in 1802, but it was not till 1807 that the complete course of sixty lectures was published in two quarto volumes. They were republished in 1845 in octavo, with references and notes by Professor Kelland. Among the subjects treated in these lectures are mechanics, including strength of materials, architecture and carpentry, clocks, drawing and modelling; hydrostatics and hydraulics; sound and musical instruments; optics, including vision and the physical nature of light; astronomy; geography; the essential properties of matter; heat; electricity and magnetism; climate, winds, and meteorology generally; vegetation and animal life, and the history of the preceding sciences. The lectures were followed by a most complete bibliography of the whole subject, including works in English, French, German, Italian, and Latin. The following is the syllabus of one lecture, and ill.u.s.trates the diversity of the subjects dealt with:--

”ON DRAWING, WRITING, AND MEASURING.

”Subjects preliminary to the study of practical mechanics; instrumental geometry; statics; pa.s.sive strength; friction; drawing; outline; pen; pencil; chalks; crayons; Indian ink; water-colours; body colours; miniature; distemper; fresco; oil; encaustic paintings; enamel; mosaic work. Writing; materials for writing; pens; inks; use of coloured inks for denoting numbers; polygraph; telegraph; geometrical instruments; rulers; compa.s.ses; flexible rulers; squares; triangular compa.s.ses; parallel rulers; Marquois's scales; pantograph; proportional compa.s.ses; sector. Measurement of angles; theodolites; quadrants; dividing-engine; vernier; levelling; sines of angles; Gunter's scale; Nicholson's circle; dendrometer; arithmetical machines; standard measures; quotation from Laplace; new measures; decimal divisions; length of the pendulum and of the meridian of the earth; measures of time; objections; comparison of measures; instruments for measuring; micrometrical scales; log-lines.”

This represents an extensive area to cover in a lecture of one hour.

When Newton, by means of a prism,

”Unravelled all the s.h.i.+ning robe of day,”

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