September i, 192 i] 



NATURE 



the two published papers on electricity. In addi- 

 tion, Clerk Maxwell's introduction and notes ex- 

 tend over more than 100 pages, and form a per- 

 manent record of his work on the manuscripts. 

 The new edition of the electrical researches, 

 which now forms vol. i of the " Scientific Papers," 

 has been prepared by Sir Joseph Larmor, who 

 has added a preface and a number of notes such 

 as were needed to bring Clerk Maxwell's com- 

 mentary up to date, and has made a number of 

 improvements in the text as issued just before 

 the death of the first editor. 



The chemical and dynamical researches which 

 form the second volume of the " Scientific Papers " 

 are edited by Sir Edward Thorpe, and have not 

 been issued previously. In this case the propor- 

 tion of published papers is much larger, but the 

 seventy-four pages of introduction form a masterly 

 review of Cavendish's work as a chemist, and 

 bring out in a remarkably clear way some of the 

 main features of this work. Thus it appears, not 

 only from the papers, but also from the manu- 

 scripts, to how large a degree Cavendish's ex- 

 periments assumed an accurately quantitative 

 character — even the alkalis that he used were 

 standardised by neutralising with nitric acid and 

 weighing the nitre which they yielded on evapora- 

 tion. It was perhaps this passion for exact 

 measurements that caused him to withhold from 

 publication much of his experimental work, as, 

 for instance, part 4 of his " Experiments on 

 Factitious Air," in which he studied with much 

 care, but without securing completely consistent 

 measurements, the mixtures of gases (carbon 

 monoxide and dioxide, marsh-gas, and hydrogen) 

 produced by the destructive distillation of wood, 

 tartar, and hartshorn. 



A second feature to which the editor directs 

 much attention is Cavendish's adhesion to the 

 doctrine and language of the phlogiston theory. 

 The doubt as to Cavendish's claim to the discovery 

 of the composition of water, which is indisputable 

 as a matter of experiment, rests mainly on the 

 ambiguous expression of his results in the lan- 

 guage of this theory. Those who have read his 

 published papers are familiar with the necessity 

 that exists for thinking of oxidation when Caven- 

 dish speaks of dephlogistication ; but it is perhaps 

 fortunate that the letter written by Cavendish to 

 Blagden on the receipt of a copy of Lavoisier's 

 "Nomenclature Chymique " was not published at 

 the time, for it contains a strong protest against 

 naming substances in terms of a theory, a pro- 

 test which is scarcely justified from one whose 

 writings, almost from beginning to end, require 

 to be translated mentally, in order to disentangle 

 NO. 2705, VOL. 108] 



them from the language of an obsolete theory 

 in terms of which they are expressed. 



The unpublished manuscripts on chemistry con- 

 tain a considerable amount of valuable material. 

 An unpublished paper describing Cavendish's 

 " Experiments on Arsenic " (probably made in 

 1767) shows that he was familiar with the oxida- 

 tion by nitric acid of white arsenic to arsenic 

 acid, and that he had fully investigated the pro- 

 perties of the latter acid and its salts, probably 

 ten years before Scheele. He considers, however, 

 that "the only difference between plain arsenic 

 and the arsenical acid is that the latter is more 

 thoroughly deprived of its phlogiston than the 

 former," and does not recognise the significance 

 of the gain in weight which he had found to 

 accompany the oxidation. His unpublished " Ex- 

 periments on Tartar " also compete in interest 

 with the paper in which Scheele, in 1769, first 

 described the properties of the acid; but it is not 

 clear whether Cavendish's two series of experi- 

 ments preceded and followed the publication of 

 this paper, or were all carried out independently 

 of it. A note on the "Solution of Metals in 

 Acids," which was withheld from the first paper 

 on "Factitious Air," explains the action of nitric 

 acid in dissolving metals as due to the "affinity 

 of the phlogiston of the metals to the nitrous 

 acid," giving rise to vapours "composed of the 

 nitrous acid united to the phlogiston of the metal." 

 The influence of phlogiston also appears in Caven- 

 dish's increduhty when he found that charcoal 

 deflagrated with nitre showed a loss in weight 

 which was smaller than the loss of weight when 

 the carbonate of the ash was decomposed by 

 acids — from his point of view the "fixed air" in 

 the ash was wholly derived from the charcoal by 

 a mere process of dephlogistication, and the 

 oxygen contributed by the nitre was not allowed 

 for ; in the same way, it may be noted, Lavoisier 

 at first tried to recover oxygen from mercuric 

 oxide by heating it with charcoal — a phlogisti- 

 cating agent the material character of which was 

 realised only when at last the theory of phlogiston 

 was obliged to release its strangle-hold on the 

 growing science of chemistry. 



One other service which the editor of the 

 chemical and dynamical researches has ren- 

 dered to the vindication of the merits of Caven- 

 dish as a pioneer worker in science is seen in his 

 detailed study of the experiments on the freezing 

 of aqueous acids, which Cavendish carried out 

 with the co-operation of Mr. John McNab, of 

 Albany Fort, Hudson Bay, as described in the 

 Philosophical Transactions of 1788. Sir Edward 

 Thorpe is able to show, by a comparison with 



