44 



NATURE 



[September 12, 191 2 



a heavy red liquid which he believed to be a chloride 

 of iodine. He found the properties to be different in 

 many respects from chloride of iodine ; still, he was 

 able to satisfy all his doubts, and he put the liquid 

 aside. Some months later he received Balard's paper 

 announcing the discovery of bromine, w'hich he recog- 

 nised at oiice as the red liquid which he had previously 

 prepared and studied. Thus, though imagination is 

 indispensable to a chemist, and though I think 

 chemists should be, and let us hope are, poets, or at 

 least possess the poetic temperament, still, little can 

 be achieved without a thorough laboratory training ; 

 and he who discovers an improved experimental 

 method or a new differentiating reaction is as surely 

 contributing to the advancement of science as he who 

 creates in his imagination the most beautiful and 

 promising hypothesis. 



It may never be possible to trace in civilisation's 

 early records the e.Kact period and place of the origin 

 and beginnings of our science, but the historical 

 student has been led, it appears to me, by a sure 

 instinct to search for this in such lands of imagina- 

 tive story as ancient Egypt and Arabia. For is there 

 anything more fittingly comparable with the mar- 

 vellous experiences of a chemical laboratory than the 

 wonderful and fascinating stories that have come down 

 to us in "The Arabian Nights"? Those monuments 

 of poetic building of which Burton, in the introduc- 

 tion to his great translation, says that in times of 

 official exile in less-favoured lands, in the wilds of 

 Africa and America, he was lifted in imagination by 

 the jinn out of his dull surroundings, and was borne 

 off by him to his beloved Arabia, where under 

 diaphanous skies he would see again "the evening 

 star hanging like a golden lamp from the pure front 

 of the western firmament ; the after-glow transfigur- 

 ing and transforming as by magic the gazelle-brown 

 and tawny-clay tints and the homely and rugged 

 features of the scene into a fairyland lit with a light 

 which never shines on other soils for seas. Then 

 would appear," &c. I cannot help thinking that the 

 study of such books as this, the habit of exercising 

 the imagination by reconstructing the scenes of beauty 

 and enchantment which they describe, might do much 

 to strengthen and sharpen the imaginative faculty, 

 and greatly increase its efficiency as an indispensable 

 tool in the hands of the pioneer who seeks to extend 

 the boundaries of knowledge. The Times, in the 

 leading article already quoted, says that, as with a 

 Shakespeare, "it is the same with imaginative dis- 

 coverers in science. . . . But the faculty is not merely 

 a fairy gift that can be exercised without pains. As 

 the sense of right is trained by right action, so the 

 sense of truth is trained by right thinking and by all 

 the labour which it involves. That is as true of the 

 artist as of the man of science ; and one of the greatest 

 achievements of science has been to prove this fact 

 and so to justify the imagination and distinguish it 

 from fancy." 



.'\gain, let it not be forgotten that chemistry in its 

 highest sense — that is, in its most general and useful 

 sense — is purely a w-orld of the imagination, is purely 

 conceptual. And in addition to this, moreover, it is 

 based, like all science, on the underlying assumption 

 of the uniformity of Nature, an assumption incapable 

 of proof. If we think of tlie science as a body of 

 abstract general theory, and exclude for the moment 

 from our purview its innumerable practical applica- 

 tions, and also all special individual facts not yet 

 known to be related to general theorv, then what 

 remains are the more or less general facts or laws. 

 These it is which give the power of prediction in 

 newly arising cases of a similar character; the power I 

 of foresight by which the claim of chemistry to its 

 position as a science is justified. Chemistry, as such, I 

 NO. 2237, VOL. 90] 



is a complicated ideal structure of the imagination, a 

 gigantic fairy palace, and, be it noted, can only con- 

 tinue to exist so long as there are minds capable of 

 reproducing it. Think of all the speculation — and- 

 speculation too of the highest utility when translated 

 into concrete applications — about the internal struc- 

 ture of molecules. I venture to say that the most 

 magnificent creations of the world's greatest archi- 

 tects are not more elaborate or more beautiful or more 

 fairylike than the chemist's conception of intra- 

 molecular structure and the magical transformations 

 of which molecules are capable ; and yet no one has 

 had direct sensuous experience of any molecule or 

 atom, or possibly ever will. It is well from time to 

 time to recall these truths and realise where we are. 

 But although the conceptual nature of science is un- 

 questionable, it certainly contains truth in some form 

 as tested by deductive concrete realisation, by correct- 

 ness of prediction, and during the last century or two 

 has undoubtedly given to man a mastery over Nature 

 never before dreamt of. 



A Brief Historical Retrospect. 

 The foundations of chemistr}', as we now know it, 

 were laid under the influence, the guidance, of three 

 great theories : first, the theory of the alchemists of 

 the transmutation of metals by means of the philo- 

 sopher's stone; second, the theory of phlogiston, con- 

 nected so much with the names of Becher and Stahl, 

 w'hich held sway for some two centuries ; third, the 

 theory of combustion, the quantitative period of 

 chemistry, inaugurated by the great Scottish chemist 

 Black by his introduction of the balance. How this' 

 led to a veritable renascence of chemistry in the hands 

 of Lavoisier and the other giants of that stirring 

 period — the close of the eighteenth and commence- 

 ment of the nineteenth centuries — is well known. 

 Looking back at the warfare w'hich was waged about 

 these older theories, for and against them, one realises" 

 now that there were elements of truth on both sides ; 

 for have we not in the work of Sir William Ramsay 

 and others the revival of transmutation, and does not 

 the essential truth of phlogiston survive in the modern 

 doctrine of heat? In one of Dr. Johnson's letters to 

 Boswell there is a curious reference to transmutation. 

 He says that a learned Russian had at last suc- 

 ceeded, but, fearing the consequences to society, he 

 had died without revealing the secret. 



After the discovery of o.xygen and the beginnings 

 of quantitative chemistry, the science was ready for 

 Dalton's great discoveries respecting combination by 

 weight ; the corresponding discoveries by Gay-Lussac 

 on combination of gases by volume, and, through the 

 latter, for Avogadro's famous hypothesis. Dalton had 

 indeed, by reviving an old Greek suggestion, pro- 

 posed to explain his discoveries by his atomic theory, 

 but neither this nor our molecular theory, though the 

 latter was inherent in the laws of gaseous combina- 

 tion of Gay-Lussac and in Avogadro's hypothesis, 

 was finally put upon its present basis until Can- 

 nizzaro took up the subject half a century later. Mean- 

 while Dulong and Petit had completed their studies of 

 atomic heat, and Mitscherlich had pointed out the 

 relation between isomorphism and molecular structure. 

 When it is considered how little is known of solid or 

 liquid structure, and that our present knowledge of 

 molecules is only of gaseous molecules, it is fortunate 

 that these methods of study of solids are available. 

 The same may be said of the results of the w-ork of 

 Kopp and his successors on molecular volumes. Of 

 other aids to fixing our conception of molecules and 

 atoms I need only refer to the periodic law, the 

 studies of the properties of dilute solutions, of electro- 

 lytic dissociation, and of surface tension of liquids. 

 Liebig, in his first inquiry, begun before he went 



