NA TURE 



153 



GRAHAM'S RESEARCHES 



Chemical and Physical Researches. By Thomas Graham, 

 D.C.L., F.R.S. Collected and printed for presentation 

 only. (Edinburgh, 1876.) 



IT is but seldom that science owes a work like this to 

 private munificence. All, therefore, to whom Mr. 

 Graham's memory is dear will be specially grateful to 

 Mr. James Young for choosing, as the second monument 

 he has raised to his friend, the publication of this splendid 

 volume. 



It is fortunate also that its compilation has been under- 

 taken by Dr. Angus Smith, who has done more than 

 collect the scattered writings, for he has added an analysis 

 of the contents of the volume which cannot fail to be of 

 use, and reminds us, in a careful preface, of Graham's 

 cloim to a place in "that chain of eminent thinkers which 

 has been represented by such as Leucippus, Lucretius, 

 Newton, Higgins, and Dalton." As the work is printed 

 for private circulation only, it may be well to give a brief 

 summary of this preface which is headed " Graham and 

 other Atomists." 



A sketch is first given of the nature of Indian and 

 Greek thought as regards atoms, and, passing to Leu- 

 cippus, Dr. Smith points out that " in the mind of this 

 early Greek, the action of the atom as one substance 

 taking various forms by combinations unlimited, was 

 enough to account for all the phenomena of the world." 

 Leucippus told us that all was motion. ■' Graham con- 

 ceived the idea that the diversity in the motion was the 

 only basis of the diversity of the material, or that an atom 

 constituted an element of a special kind," according to 

 the velocity or nature of its movements. After Leucippus 

 few men seem to have devoted much attention to the 

 subject until modern times. A quotation from Lange 

 gives the position assumed by Democritus, "The differ- 

 ence of substances arises from the difference in the number, 

 size, shape, and arrangement of the atoms. The atoms 

 have no internal conditions ; they act by pressure and per- 

 cussion only." 



Dr. Smith considers that the views of Lucretius de- 

 serve attention, as he was the only full expositor of the 

 theory of atoms to the ancients. To Lucretius atoms are 

 " solid and eternal, with some unalterable motion.'' 

 "They are made of parts, which parts cannot exist by 

 themselves." " Motion is to him everything that can be 

 found in life and thought, which are only the clashing of 

 atoms." This theory allows of any shape of molecules, 

 even hooked ones, which, as Dr. Smith somewhat dryly 

 adds, " are spoken of as explaininj^ combination both in 

 Lucretius and more modern writers." Space will not 

 permit Newton's words to be given at length, but he 

 held that the primitive particles of which matter is com- 

 posed are incomparably hard and incapable of wear, for 

 otherwise " water and earth composed of old worn 

 particles, would not be of the same nature and texture 

 now with water and earth composed of entire particles in 

 the beginning." He is thus forced to the conclusion that 

 " the changes of corporeal things are to be placed only in 

 V»L. XV. — No. 373 



the various separations and new associations and motions 

 of these permanent particles." 



A sketch is then given of the next important stage, 

 namely, the motion of gaseous molecules, beginning 

 with Daniel Bernoulli, and passing to Davy, Rumford, 

 and Herapath — to whom, by the by, Graham asserted in 

 1863 the merit of reviving Bernoulli's hypothesis in 

 modern times is fairly due. As is well known, the theory 

 of gases now generally received makes them consist of 

 small bodies continually impinging on one another, and 

 on the walls of the inclosing vessel, their elasticity in- 

 creasing with the temp?rature, and the pressure of the 

 gas being due to the impact of the particles against any 

 surface presented to them, an hypothesis which Joule 

 investigated experimentally. 



Now, as Dr. Smith shows, "it was the object of Graham's 

 life to find out what the movement of an atom was. . . . 

 He avoided picturing the most primitive motion in all its 

 character, but he seems to indicate one of revolution, as 

 he brings in the similarity to the orbit of a planet," and 

 he advances still further, " when he adopts the theory of 

 one kind of matter, each atom being distinguished by the 

 extent of its motion," there being an initial impulse for each 

 kind. " These atoms are believed to be congregate . . . and 

 equal volumes can coalesce and form a new atomic group." 

 Indeedthe whole force of Graham's intellect was patiently 

 and persistently devoted to this study of molecular move- 

 ment, and as Dr. Smith claims him to be as " strict an 

 anatomist as perhaps can Ije found," it may be interesting 

 to gather from his writings some of the passages in which 

 his views are expressed. 



His earliest paper, on the Absorption of Gases by Liquids, 

 was published in Thomson's " Annals of Philosophy," in 

 1826, In it he considers that "gases may owe their 

 absorption in liquids to their capability of being liquefied," 

 and that when gases appear to be absorbed by liquids, 

 they are simply reduced to that liquid inelastic form, 

 which otherwise (by cold or pressure) they might be made 

 to assume ; their detention in the absorbing liquid is 

 owing to that mutual affinity between liquids which is so 

 common. In his last paper in the Phil. Trans., pub- 

 lished forty years afterwards, he refers to the liquefac- 

 tion of gas in colloids in much the same terms, for he 

 alludes to the " general assumption of liquidity by gases 

 when absorbed by actual Hquids or by soft colloids," and 

 he states that those gases penetrate (india-rubber) most 

 readily which are easily liquefied by pressure, that gases 

 undergo liquefaction when absorbed by liquids and such 

 colloid substances as india-rubber, and finally, that the 

 complete suspension of the gaseous function during the 

 transit through india-rubber cannot be kept too much in 

 view. 



The Quarterly yournal of Science, 1829, pp. 74-83, 

 contains his first paper on the diffusion of gases. In it 

 he states that the diffusiveness of gases is inversely as 

 some function of their density, apparently the square-root 

 of the density ; he also considers it conceivable that orifices 

 of excessive minuteness may be altogether imoassable by 

 gases of low diffusive power, but defers these theo- 

 retical considerations to a future paper. This promise 

 was fulfilled by a paper in 183 1, the object of which was 

 to establish the following law of the diffusion of gases. 

 " The diffusion or spontaneous intermixture of two gases 



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