April i6, 1896] 



NATURE 



555 



these passages may be quoted as a fait example both 

 of the author's style and of the interesting subjects he 

 discusses. 



"Are not all our efforts, whether prompted by 

 philanthropic or religious zeal, by which we seek to 

 protect and preserve the aboriginal races of the New- 

 World, wholly mistaken ? Are they not in effect 

 absolutely murderous? We gather them into close 

 school-rooms and churches, where teachers and mis- 

 sionaries speak to them from infected lungs. We en- 

 deavour to persuade them to abandon their nomadic 

 habits and form settled communities. We— and thereby 

 we prove our own barbarism, the imperfection of our own 

 civilisation — force them in climates where clothes are 

 wholly unnecessary, and therefore a species of dirt, to 

 wear clothes, than which a better vehicle for air and 

 earth-borne disease cannot be well conceived. In fact 

 we strive to bring them at one bound into that state of 

 society which has become possible to us only at the cost 

 of tens of millions of lives during thousands of years." 



There are a few errors and perhaps some fallacies in 

 this very interesting and well-written volume ; but much 

 may be forgiven in a book that is both original and 

 suggestive ; while in its thorough-going advocacy of the 

 main doctrine of . Weismann — the non-inheritance of 

 acquired characters — it affords an excellent antidote to 

 the elaborate but one-sided arguments of Prof Cope. 

 Alfrkd R. Wallace. 



THE ATOMIC THEORY AGAIN. 



A New View of the Origin of Dal tori's Atomic Theory : 

 a Contribution to Chemical History, Sr^c. By Henry 

 E. Roscoe and Arthur Harden. Pp. 191. (London : 

 Macmillan and Co., 1896.) 



La Theorie Atomique et la Theorie Dualistique. Trans- 

 formation des formules. Differences Essentielles entre 

 les deux theories. Par E. Lenoble, Professeur de 

 Chimie a I'Universite libre de Lille. Pp. 94. (Paris : 

 Gauthier-Villars.) 



THE origin of the former of these two books is well 

 explained in the following passage from the short 

 introduction : 



'•It may seem remarkable that after the lapse of 

 nearly a century since John Dalton first applied the 

 atomic theory of matter to chemical phenomena, it 

 should be possible to find anything new respecting the 

 genesis of his ideas. And this is the more remarkable 

 when we remember that the life and scientific labours of 

 the great Manchester chemist have formed the subject of 

 independent memoirs at the hands of two such able 

 contemporaries as Charles Henry and Angus Smith. 

 The explanation is to be found in the unlooked-for dis- 

 covery, in the rooms of the Literary and Philosophical 

 Society of Manchester, where the whole of Dalton's 

 experimental work was carried out, of his laboratory and 

 lecture note-books contained in a number of manuscript 

 volumes. A careful study of these has led us to con- 

 clusions concerning the origin of the atomic theory of 

 chemistry which differ widely from those which have 

 been generally accepted. It has hitherto been supposed 

 that it was the experimental discovery of the law of 

 combination in multiple proportions which led Dalton, 

 seeking for an explanation of this most remarkable fact, 

 to the idea that chemical combination consists in the 

 approximation of atoms of definite and characteristic 

 weight, the atomic theory being thus adopted to explain 

 the facts ascertained by chemical analysis. This pre- 

 vailing view is found on examination to rest upon the 



NO. 138 1, VOL. 53] 



authority of contemporary chemists, rather than on any 

 explicit statement on the part of the author himself; for, 

 strange as it may appear, no attempt to explain the 

 genesis of his ideas is to be found in any of Dalton's 

 published writings." 



It now appears that Dalton was probably led to his 

 theory by an attempt to apply the Newtonian doctrine 

 of the atomic constitution of matter to the explanation 

 of the physical properties of gases, and more especially 

 to the case of the gases present in atmospheric air. 



The evidence upon which this conclusion is based is 

 derived partly from the newly-discovered manuscript 

 notes of a course of lectures given by Dalton at the 

 Royal Institution in London early in 18 10. In the 

 course of these he says that it was the consideration of 

 the constitution of mixed elastic fluids which led him to 

 contemplate the effect of differences of size in the 

 particles, and thus "it became an object to determine the 

 relative sizes and weights, together with the relative 

 numbers of atoms in a given volume. This led the way 

 to the combinations of gases, and to the number of atoms 

 entering into such combinations. . . . Thus a train of 

 investigation was laid for determining the number 

 and -weight of all chemical elementary principles which 

 enter into any sort of combination one with another." 

 This is a statement of Dalton's own recollection of the 

 course of events after the lapse of seven or eight years 

 from the time when he made his first attempts at 

 estimating atomic weights. To this must be added the 

 fact that the first part of his " New System of Chemical 

 Philosophy," published in 1808, contains no account of 

 any chemical analyses, and in the short chapter on 

 chemical synthesis, at the end of this first part, the author 

 speaks of the application of certain general rules which 

 he lays down " to the chemical facts already well ascer- 

 tained," the experiments conducted by himself being 

 reserved for part ii., published two and a half years later. 



On the other hand, Dr. Thomas Thomson, after a visit 

 to Dalton in 1804, makes the very definite statement 

 upon which chemists have generally relied. He says : 

 " Mr. Dalton informed me that the atomic theory first 

 occurred to him during his investigations of olefiant gas 

 and carburetted hydrogen gas." If this was the im- 

 pression carried away by an interested visitor at the time 

 when Dalton was occupied by the earlier stages of his 

 investigations, it is impossible to avoid the conclusion 

 that there was some foundation for it. Dalton was 

 occupied with the idea of atoms, their relative sizes, &c., 

 from 1 801. In the summer of 1804 he collected and 

 analysed the gas from ponds (" System Chem. Phil.," 

 p. 445). In 1805, he says (MS. Lecture 17, p. 16 in the 

 book) the idea occurred to him that the sizes of the par- 

 ticles of elastic fluids must be different. We cannot, 

 therefore, admit that the authors have fully made out 

 their case, though it does appear probable that the idea 

 of atomic structure was growing in Dalton's mind before 

 he made any chemical analyses for himself ; but whether 

 it had taken the final definite shape in which it appears 

 in the notes of the lectures at the Royal Institution, and 

 in the " New System of Chemical Philosophy," appears 

 to us to be still open to question. 



The second book on our list is a production of wholly 

 different type. This little volume explains how to trans- 



