Septemijer 12, 1895J 



NA TURE 



477 



up of constant elements like his electrons, whose periods are 

 necessarily all alike. It is possible that the vortex cell theory of 

 the ether, of which I have already spoken, may suffice to ex- 

 plain ^gravitation also. The cells, besides their rotational 

 rigidity, have, in addition, as we saw, a peculiar elasticity of 

 form. To get an idea of how this theory may account for 

 weight, let us suppose the simplest case where all the cells are 

 exactly alike, and the medium is in equilibrium. Now suppose 

 one of the cells begins to grow. It forces the medium away on 

 all sides ; the cells will be distorted in s(.>me definite way, and a 

 strain set up. Further, this strain will be transmitted from the 

 centre, so that the total amount across any concentric sphere wdl 

 be the same. Stresses will therefore be set up in the whole 

 medium. If a second cell begins to grow at another jjlace it 

 will produce also a state of strain, the total strain depending on 

 the presence of both. The stresses called into play in the medium 

 will produce a stress between the bodies, but it is questionable 

 whether it would be inversely as the square of the distance. 

 Whether it would be an attraction or repulsion can only be 

 determined by mathematical investigation. The problem is 

 quite determinate, though probably a very difficult one, and 

 would be of mathematical interest quite apart from its jjhysical 

 importance. Since apparently the phenomena of gravitation 

 have no direct interaction with those of light and electricity, 

 whilst the mind rejects the possibility of two difrei.;nt media 

 occupying the same space, we seem driven to look for it in an 

 independent structure of the same medium. .Such a structure is 

 already to our hands, with its effects waiting to be determined. 

 It may well be that it may prove to be the cause we are seeking. 

 The rapid survey I have attempted to make is no doubt a 

 medley of suppositions and inferences combined with some .sound 

 deductions. This is the necessary consequence of a prospecting 

 stirvey in a region whose surface has been merely scratched by 

 ])ioneers. My object has been to .show that this theory of an 

 ether, based on a |)rimitive perfect fluid, is one which shows very 

 promising signs of being able to explain the various phy.sical 

 phenomena of tnir material universe. I'robably, nay certainly, 

 the explanations suggested are not all the true ones. Some will 

 have to be given up, others modified with further knowledge. 

 We cannot proceed to particularise in our secondary hypotheses 

 until we know more about the properties of such media as we 

 have been considering. Every special problem solved in vor'ex 

 motion puts us in a position to form clearer ideas of what can and 

 what cannot happen. The whole question of vortex aggregates 

 and their interaction.s is practically untouched, and a rich field 

 is open for mathematical investigation in this portion only of 

 the subject. In all cases, whether a fluid ether is an acttial fact 

 (jr not, the results obtained will be of sjiecial iiUerest as types of 

 fluid motion. It is at present a .subject in which the mathe- 

 maticians must lead the attack. I shall have attained my object 

 in choosing this .subject for my address, if by it I can induce 

 some of our younger mathematicians to take it up and work out 

 its details. 



SECTION B. 



CHEMISTRY. 



Openinc. Address by Prok. Rai'h.vel Mei.dola, F.R.S., 

 K.I.C., For. Sec. C.S., President of the Section. 



The State of Chemical Science in 1851. 



In order to estimate the progress of chemical science since the 

 year 1X5 1, when the Hritish .\ssociation last met in this town, it 

 will be of interest for us to endeavour to place ourselves in the 

 position of those who took part in the proceedings of Section B 

 on that occasion. Perhaps the best way of performing this retro- 

 grade feat will be to confront the fundamental doctrines of 

 modern chemistry with the state of chemical theory at that 

 |)eri<Kl, because at any point in the history of a .science the 

 theoretical conceptions in vogue -whether these conceptions 

 ha\e survived to the present time or not — may lie taken as the 

 abstract summation of the facts, i.e. of the real and tangible 

 knowledge existing at the period chosen as the standard of 

 reference. 



W'ilhout going too far back in lime I may remind you that in 

 181 1 the atomic theory of the chemists was grafted on to the 

 kindred science of physics through the enunciation of the law 

 a.s.sociate(l with the name of .Vvogadro di (Juaregna. The 

 rationalising of this law had been accomplished in 1845, but the 



NO. 1350, VOL. 52] 



kinetic theory of gases, which had been foreshadowed by D. 

 Bernoulli in 1738, and in later times by llerapath. Joule, and 

 Kronig, lay buried in the archives of the Royal .Society until 

 recently unearthed by Loril Rayleigh and given to the world in 

 1892 under the authorship of Waterston, the legitimate dis- 

 coverer. The later develo])ments of this theory ilid not take 

 place till after the last Ipswich meeting, viz. in 1857-62, by 

 Clau.sius, and by Clerk Maxwell in 1860-67. Thus the kinetic 

 theory of ga.ses of the physicists had not in 1851 .acquired the full 

 significance for chemists which it now possesses : the hypothesis 

 of .\vogadro was available, analogous conceptions hati lieen 

 advanced by Davy in 1812, and by .Vmiicrc in 1S14; but no 

 substantial chemical reasons for its adoption were adduced until 

 the year 1846, when Laurent published his work on the law of 

 even numbers of atoms and the nature of the elements in the free 

 state (Ann. Chim. Phys. [3], 18, 266). 



The so-called " New Chemi.stry" with which .students of the 

 present time are familiar was, in fact, being evolved about the 

 periotl when the British .\ssociation last as.sembled at Ipswich ; 

 but it was not till some years later, and then chiefly through the 

 writings of Laurent and Gerhardt, that the modern views be- 

 came accepted. It is of interest to note in passing that the 

 nomenclature of organic compounds formed the subject of a 

 report by Dr. Daubeny at that meeting in which he .says : — *' It 

 has struck me as a matter of surprise that none of the British 

 treatises on chemistry with which I am acquaintei.1 should con- 

 tain any rules to guide us, either in aftixing names \o substances 

 newly discovered or in divining the nature and relati<ms of bodies 

 from the appellations attached to them. Nor do I find this 

 deficiency supplied in a manner which to me appears satisfactory 

 when I turn to the writings of continental cheinists. " In a sub- 

 sequent portion of the report Dr. Daubeny adds : — " No name 

 ought, for the sake of convenience, to exceed in length six or 

 seven syllables.'' I am afraid the requirements of modern 

 organic chemistry have not enabled us to comply with this 

 condition. 



Among other physical discoveries which have exerted an im- 

 portant influence on chemical theory the law of Dulong and 

 Petit, indicating the relationship between specific heat and 

 atomic weight, had been announced in 1819, had been subse- 

 quently extended to compounds by Neuni.ann, and still later had 

 been jilaced upon a sure basis by the classical researches of Reg- 

 nault in 1839. But here, again, it was not till after 1851 that 

 Cannizzaro ( 1858) gave this law the imp(»rtance which it now 

 possesses in connection with the determination of atomic 

 weights. Thermo-chemistry as a distinct branch of our science 

 may also be considered to have arisen since 1S51, although th» 

 foundations were laid before this period by the work of Kavre 

 and .Silbermann, .Andrews, (iraham, and especially Hess, who.se 

 inqiortant generalisation was announced in 1S40. ami whose 

 claim to just recognition in the history of phy.sical chemistry has 

 been ably advocate<l in recent limes by Ostwald. But the 

 elaboration ofthermo-chemical facts and views in the light of 

 the dynamical theory of heal was first connuenced in 1853 by 

 Julius Thomsen, and has since been carried on concurrently with 

 the work of Berthelot in the same field which the latter investi- 

 gator entered in 1865. Electro-chemistry in 1851 was in an 

 equally rudimentary condition Davy had jniblishe^l his electro- 

 chemical theory in 1807, and in 1812 Berzelius had put forward 

 those views on electric aftinity which became the basis of his 

 dualistic system of formulation. In 1S33 Faraday announced 

 his famous law of electro-chemical equivalence, which gave a fatal 

 blow to the conceptiim of Berzelius, and which later (1839 40) 

 was made use of by Daniell in order to show the imienability of 

 the dualistic sy.stem. By 1851 the views of Berzelius had been 

 abandoned, and, so far as chemical theory is concerned, the 

 whole subject may be considered to have been in abeyance at 

 that lime. It is of interest to note, however, that in thai ye<ar 

 Williamson advanced on quite distinct grounds his now well- 

 known theory of atomic interchange between molecules, which 

 theory in a more extended form was developed independently 

 from the physical side and applied to electrolytes by Clausius in 

 1857. The modern theory of electrolysis associaleil with the 

 namesof .\rrhenius, van't llofl', and Ostwald is of comparatively 

 recent growth. It appears that Hillorf in 187S was the first to 

 point out the relationship between electrolytic conductivity and 

 chemical activity, this same author as far back as 1856 hrfving 

 combated the prevailing view that the electric current during 

 electrolysis does the work of overcoming the affinities of the ions. 

 .\rrheniHS formulated his theory of electrolytic dis.sociation in 



