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    JtJLT 28, 1855.] T H E L E A £> E R. *a ...

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    THE MANHOOD OF NEWTON. Memoirs of the Li...

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    Jtjlt 28, 1855.] T H E L E A £> E R. *A ...

    JtJLT 28 , 1855 . ] T H E L E A £ > E R . * a K *

    The Manhood Of Newton. Memoirs Of The Li...

    THE MANHOOD OF NEWTON . Memoirs of the Life , Writings , and Discoveries of Sir Isaac Newton . By Sir David BrewBter . Constable and Co . ( SECOND ARTICLE . ) Ik a former article wo rapidly ran through the Boyhood of the illustrious philosopher , showing the traces of the truth " The Child is Father to the Man . " With the epoch of Boyhood ceases what may be called the purely biographic interest of these volumes : the man retires into the background , the philosopher usurps the scene . Not that Sir David Brewster has failed in collecting far and wide some biographical details , crushing by the way some noDular errors , but the biography ceases to be interesting . We nro . rAnd tn

    learn that Newton s alleged insanity was only a brief illness ; we are not sorry to learn that the old story about his dog Diamond destroying his papers , but not thereby ruffling his temper , is a pure fiction , Newton never having kept u dog ; we arc glad to bo put right respecting the composition of his theological writings , and we follow with some eagerness the history of the disputes with Leibnitz and Hanisteed ; but the biography , as a biography , is not interesting ; and although criticism may have much to say to the wide latitude of digression Sir David has allowed himself , it is certain that the most valuable portions of these bulky volumes are those pages which relate to Newton ' s discoveries and the sciences he so magnificently illus - trated .

    It is worthy of remark that Newton , who , as his mathematical rival , Leibnitz , confessed , ! ia < l done : is much as all the mathematicians who preceded him put together , began his studies by a contempt of Euclid ! He had purchased a book on Judicial Astrology , and finding he could not understand the figure of the heavens without a knowledge of trigonometry , hegot a copy of Euclid with an index of nil the problems at the end , and Having turned to two or three which lie thought likely to remove his difficulties , he foond the truths which they enunciated so self-evident , that he expressed his astonishment that any person should have token the trouble of writing a demonstration of

    them . He , thereforf , threw aside Euclid " asa trifling book , " and set himself to the study of Descartes' ( Jeometry , where problems not so aim pie seem to have baffled hU ingenuity . Even after reading a few pages , he got beyond his depth , and laid aside the work ; and he is said to have resumed it again and again , alternately retreating and advancing till he was master of the whole , without having received any assistance . The neglect which he had shown of the elementary truths of geometry lie afterwards regarded as a mistake in his mathematical studies ; and on a future occasion he expressed to Dr . Pemberton his regret that " he had applied himself to the works of Descartes , and other algebraic writers , before he had considered the Elements of Euclid with that attention which so excellent a writer deserved . "

    In four years afterwards he made his discovery of Fluxions I The first gleam of the discovery of gravitation is thus recorded by Sir David : — It was doubtless in the same remarkable year 1666 , or perhaps in the autumn of 1665 , that Newton ' s mind was first directed to the subject of gravity- He appears to have left Cambridge some time before the 8 th of August , 1665 , when the College was " dismissed" on account of the Plague , and it was , therefore , in the autumn of that year , and not in that of 1 C 66 , that the apple is said to have fallen from the tree at Woolsthorpe , and suggested to Newton the idea of' gravity . When sitting alone in tho garden , and speculating on the power of gravity , it occurred to him that as the same power by which the apple fell to the ground was not sensibly diminished at the greatest distance from the centre of the earth to which we can reach , neither at the summits of the loftiest spires , nor on the tops of the highest mountains , it might extend to the moon and retain her in her orbit , in the same manner as it bends into a curve a stone or a cannon-ball , when projected in a straight line from the surface of the earth . If the moon was thus kept in her orbit by gravitation to the earth , or , in

    other words , its attraction , it was equally probable , he thought , that the planets were kept in their orbits by gTavitnting towards the sun . Kepler had discovered the groat law of the planetary motions , that th « squares of their periodic times were as the cubes of their distances from the sun , and hence Newton drew the important conclusion that the force of gravity or attraction , by which the planets were retained in th « ir orbits , varied as the square of their distances from the sun . Knowing the force of gravity at the earth ' s surface , he was , therefore , led to compare it with the force exhibited in the actual motion of the moon , in a circular orbit ; but having assumed that the distance of the moon from tho earth was equal to sixty of the earth ' s semidiameters , he found that the force by which the moon was drawn from its rectilineal path in a second of time wag only 13-9 feet ^ whereas at the surface of the earth it "was 16 * 1 in a second . This great discrepancy between his theory and what he then considered to be the fact , induced him to abandon the subject , and pursue other studies With which he had been previously occupied . Tet this positive thinker , whose name is indelibly associated with the exact aciences , paid his tribute to the age , and believed in Alchemy ;—

    Id his chemical studies , which , as we have just seen , he had recently commenced , his mind was impressed with some belief in the doctrines of alchemy , and he certainly pursued his experiments to n late period of his life , with the hope of effecting some valuable trnnsmutatioiin . Among tho subjects , therefore , to which he requests Mr . Ashton to pay attention , there are . several which indicate this tendency of his mind . He dcaircs him to observe the products of nature , especially in mine .- * , with tho circumstances of mining , and of extracting metals or minerals out of their ores , and alining them ; and , > vhut he considered as fur more important than this , he wishes him to observe if there were any transmutations-out . «» : ' one species into another , us , for example , out of iron into copper , out of one salt iuto another , or into an insipid body , & c . Such transmutations , ho adds , aro above all others worth his noting , being ttfl nws ( lucifcrous , and many tinws hicrifvroua < x / H : rini < nts too , in philosophy ! Among the particular observations ' to which ho calls tho attention of his friend , is that « f u secret

    Oertaln vitriol , which changes iron into copper , anil which is said U > be kept n for tie , lucrative purpose of effecting tlmt transmutation . He is to inquire also whether in Hungary , or in the mountains of Dohemia , tluro arc rivers whoso waters nr « Wpwgnnted with gold , dissolved by Homo corrosive fluids like aqua regis ; and whether tho practice of laying mercury in the rivers till it bo tinged with gold , and then pwatlng tho gold by straining tho mercury through leather , ho still a secret or « P «« ly practised . There wnu at . this time in Holland u notorious alchemist of the « M > Mof Bory , who , as Hir Isaac says , was some years sinco imprisoned by the 1 ope , to ordflr to extort from him secret * of great worth , both " as to medicine and proht , ^ WM * Trt > o mado hit ) cHcapo into Holland , whoro they granted him a ^ uord . " I think , WUSlr Isaac , "ho usually goes clothed jii green : pray , inquire what you can of W » n » and whether his ingenuity bo nny profit to tho Dutch J " His great discovery of tho refrnngibility of light is well told by Sir David , WllQ not Only shows tho ouutioua experimental method by which tho

    discovery was established , but also calls attention to the rare fact of this discovery being one which has never been claimed for any previous philosopher . No one had a . suspicion , not even a plausible conjecture to offer on the nature and origin of colours . Newton's discovery was a leap from absolute ignorance to demonstration ; no one had prepared the way , no one had even hinted that there might be a way . No sooner were his optical discoveries announced , than they were assailed , with the virulence which usually welcomes discovery in science ; and it is interesting and instructive to note that Newton himself refused to acknowledge the beautiful law of double refraction published subsequently by Huygens , a law founded on the finest experimental analysis ! Sir David justly criticises the current idea of Newton having exhibited extraordinary sagacity in his conjecture about the diamond

    The conjecture of Newton that the diamond " is an unctuous substance coagulated , " has been generally regarded as a proof of singular sagacity , and as an anticipation of the results of chemical analysis ; but it is certainly not entitled to such praise . Its solitary position among the oils and inflammable bodies led to the conjecture ; but had he known the refractive index and specific gravities of greenockite and octohedritf , he would have drawn the same conclusion respecting them , and been mistaken . The real inference respecting the composition of the diamond , which Newton ' s Table authorises , is not that it should consist of carbon , but of sulphur . " So then , " says he , " by the foregoing table , all bodies seem to have their refractive powers proportional to their densities ( or very nearly ) excepting so far as they partake more or less of sulphureous oily particles , and thereby have their refractive power made greater or less . Whence it seems rational to attribute the refractive power of all bodies chiefly , if not wholly , to the sulphureous particles with which they abound . For it is probable that all bodies abound more or less with sulphurs . Ajid as light congregated by a burning glass acts most upon sulphureous bodies , to turn them into fire and flame , so , Eince all action is mutual , sulphurs ought to act most upon light . "

    Those who are interested in the history of Science will read with peculiar interest the celebrated Letter to Boyle , in which Newton gives a sketch of his hypothesis of a universal ether . Here is a man who in Astronomy and Physics proceeds with the utmost caution , moving only by the guidance of experiment and clear fact , and no sooner does he approach the more complex science of Biology than he gives the rein to supposition with the wildness of a Galen or an Averrhoes . The " puzzling problem by what means the muscles are contracted and dilated to cause animal motion , " may , he thinks , have more light thrown on it by his hypothesis than by any other : ami this is the explanation : —

    First , then , I suppose there is such a spirit ; that is , that the animal spirits are neither like the liquor , vapour , or gas of spirits of wine ; but of an setherial nature , subtile enough to pervade the pnimni juices as freely as the electric , or perhaps magnetic , eflluvia do glass . And to know how the coats of the brain , nerves , and muscles may become a convenient vessel to hold so subtile a spirit , you may consider how liquors and spirits are disposed to pervade , or not pervade , things on other accounts than their subtilty ; water and oil pervade wood and stone , which quicksilver does not ; and quicksilver , m & taJs , which water and oil do not ; water and acid spirits pervade salts , which oil and spirit of wine do not ; and oil and spirit of wine pervade sulphur , which water and acid spirits do not ; so some f luids ( as oil and water ) , though their parts are in freedom enough to mix with one another , yet by some secret principle of unsociableness they keep asunder ; and some that are sociable may become unsociable by adding a third thing to one of them , as water to spirit of wine by dissolving

    salt of tartar in it- The like unsociableness may be in aetherial natures , as perhaps between the aethers in the vortices of the sun and planets ; and the reason why air stands rarer in the bores of small glass pipes , and aether in the pores of bodies , may be , not want of subtilty , but sociahleness ; and * on this ground , if the setherial vital spirit in a man be very sociable to the marrow and juices , and unsociable to the coats of the brain , nerves , and muscles , or to anything lodged in the pores of those coats , it may be contained thereby , notwithstanding its subtilty ; especially if we suppose no great violence done to it to squeeze it out , and that it may not be altogether so subtile as the main body of aether , though subtile enough to pervade readily the animal juices , and that as any of it is spent , it is continually supplied by new spirit from the heart . In the next place , for knowing how this spirit may be used for animal motion , you may consider how some things unsociable are made sociable by the mediation of a third . Water , which will not dissolve copper , will do it if the copper be melted with sulphur . Aquafortis , which will not pervade gold , -will do it by addition of a with but

    little sal-ammoniac or spirit of salt . JLead will not mix in melting copper ; if a little tin , or antimony , be added , they mix readily , an * part again of their own accord , if the antimony bo wasted by throwing saltpetre , or otherwise . And so lead , melted with silver quickly pervades and liquefies the silver in a much less heat than is required to melt the silver alone ; but if they be kept in the test , till that little substance that reconciled them be wasted or altered , they part again of their own accord . And in like manner the authorial animal spirit in a man may be a mediator between the common tether and the muscular juices , to make them mix more freely ; and so by sending a little of this spirit into any muscle , though so little as to cause no sensible tension of the muscle by its own force , yet by rendering the juices more sociable to the common external tvther , it may cause that jether to pervade the muscle of its own accord in a moment more freely and more copiously than it would otherwise do , and to recede again its freelv , so soon as this mediator of sociableness Sb retracted ; whence , according to whqt I said above , will proceed the swelling or shrinking of the muscleand consequently the animal motion depending thereon .

    , Thus may therefore the soul , by determining this authorial animal spirit or wind into this or that nerve , perhaps with as much ease as air is moved in open spaces , cause all the motions we see , in animals ; for the making which motions strong , it ia not necessary that we should suppose tho aether within the muscle very much condensed , or rarefied , by this means , but only that its spring is so very great that a little alteration of its density shall cause a great alteration in the pressure . And what is said of muscular motion may bo applied to the motion of tho heart , only with this difference , that tho spirit is not sent thither as into other muscles , but continually generated there by tho fermentation of the juices with wbich its flesh is rcplenwnea , and as it is generated , let out by starts into the brain , through some convenient <""*?*' to perform those motions iu other muscles by inspiration , which it did in ttrn nt Jl ¦* its generation . For I see not why the ferment in the heart may ™ t rawe as suoiu » spirit out of its juices , to cause those motions , as rubbing does out of a f '' j ™ V electric attraction , or burning out of fuel to penetrate glass , as Mr . iioyle naa buow ,

    and culcino by corrosion metals melted . It is well that from time to time we should bo ablo thus J * ~ o boil ^ en speculated ; from the errors of the past we may **» «»»^« J ^ J to tho present ; from the errors of a feowton we ^^ L ^ 2 T ^ 1 caution tho opinions of those to whom wo listen with tho greatest respect .

• Citation
  • Leader (1850-1860), July 28, 1855, page 725, in the Nineteenth-Century Serials Edition (2008; 2018) ncse-os.kdl.kcl.ac.uk/periodicals/l/issues/ldr_28071855/page/17/