64 Analyses of Books. [.July, 



appeared well ascertained, and, as far as I could, to assign the 

 original discoverer of each of them, and the exact source from 

 which I drew my information. It was not possible for me to accom- 

 plish completely either of these objects. Many facts escaped my 

 attention, and I fell into occasional mistakes in assigning the 

 original discoverers. These omissions and mistakes, when disco- 

 vered, were inserted or corrected in the subsequent editions ; and 

 indeed the alterations were so numerous as at last to injure in a 

 Very material degree the arrangement and unity of the work. I 

 have been more profuse in my quotations of authorities, and have 

 made a more complete collection of facts than any other chemical 

 writer that I know; and every subsequent systematic publica- 

 tion that I have seen, whether it made its appearance on the Conti- 

 nent or in Great Britain, I do not even except the present essay of 

 Mr. Higgins, drew very copious supplies from my volumes. Some 

 even copied verbatim the errors of the press. My rule was only to 

 quote authorities for facts, and only for facts well established ; and 

 1 never considered a fact well established when it was coupled with 

 a circumstance which I knew to be erroneous. Mr. Higgins' book 

 is rather theoretical than experimental, and therefore was not quite 

 in my way. It contains indeed experiments, and establishes the 

 composition of several bodies with accuracy ; but 1 could not put 

 any confidence in these determinations, because I perceived in them 

 obvious inaccuracies. Thus he establishes that sulphurous acid is 

 composed of equal weights of sulphur and oxygen ; but his proof 

 depends upon the supposition that 143 grains of oxygen gas contain 41 

 grains of water, or more than one fourth of its weight ; an opinion 

 evidently erroneous, and of course the whole of Mr. Higgins* 

 reasoning appeared to me inaccurate. He was accidentally right 

 from a complication of errors ; but I was not to blame in consider- 

 ing him as wrong. 



. In determining the composition of the compounds of azote and 

 oxygen, he was also right ; but this determination was founded on 

 no experiment that I could lay hold of; nor did I admit several of 

 the substances which he introduced as distinct compounds of azote 

 and oxygen. Hence there was nothing tangible which I could 

 introduce into my System. 



The only experiment that I would have quoted, if I had recol- 

 lected it, was the solution of iron in sulphurous acid, without the 

 extrication of any gas. This discovery belongs to Mr. Higgins, 

 and has been unjustly claimed by Vauquelin; though 1 dare say this 

 distinguished chemist, of whose honesty I have a high opinion, was 

 not aware of what Mr. Higgins had done when he published his 

 analysis of steel. It was very natural to try the effect of sulphurous 

 acid on iron, and therefore the fact might easily be discovered by 

 various persons, without communication with each other. But that 

 1 had no desire to bury Mi. Higgins' book in oblivion, will be 

 obvious from this circumstance, that I recommended the perusal of 

 it several years ago to Sir H. Davy, and expressed a hope that the 



