142 Anah/sis of Sciefitijic Books, 



of sentiment, are among the finest ever made; and it is dis- 

 creditable to Dr. Thomson, and detrimental to his readers, 

 that he has entirely suppressed them. In his meagre descrip- 

 tion of chlorine, his usual inaccuracy accompanies him : " when- 

 ever any vegetable blue colour is exposed to the action of 

 chlorine, it is immediately destroyed, and cannot afterwards be 

 restored by any method whatever." The gas itself cannot effect 

 this change on di-y colours ; the agency of moisture is re- 

 quired. 



" The deutoxide of chlorine was discovered about the same 

 time by Sir H. Davy and Count Von Stadion, of Vienna ; but 

 Davy's account of it was published sooner than that of Count 

 Von Stadion." The account of the former was published in 

 Thomsons Annals, eight months before that of the latter ap- 

 peared. Surely, some qualm of conscience must have smit- 

 ten our compiler, in writing his next page. " But the pro- 

 perties of the substance described by the Count, differ so 

 much from those of the gas examined by Davy, that it is 

 probable they are distinct substances." 



" A vdlume of chlorine may be considered as equivalent 

 to an atom, while a volume of oxygen gas is equivalent to 

 two atoms. Hence, if a body be a compound of two volumes 

 chlorine and one volume oxygen, we know that it consists 

 of one atom chlorine and one atom oxygen*." Into such 

 atomical inconsistencies does he fall, in following Mr. Dalton's 

 hypothesis, instead of the experimental system of Sir H. 

 Davy. 



The third section discusses iodine. It is word for word 

 the same as in the 5th edition, and it is badly extracted 

 from the memoirs of Sir H. Davy and M. Gay-Lussac. He 

 introduces here, among simple substances, his whole account 

 of iodic and chloriodic acids, in violation of his own sys- 

 tematic arrangement; and perverts. Sir H. Davy's results on 

 chloriodic acid, to suit his own atomic notions. 



Mis' fourth section on fluorine is a misnomer. It is occu- 

 pied almost wholly with fluoric acid, which being, according 

 to him, a compound, has no business among simple sub- 

 stances. His account of it is remarkable, as usual, for dis- 

 torting Sir H. Davy's results. " From an experiment of 

 Sir H. Davy," says he, " it would appear, that the number 

 which represents an atom of this acid is 1.0095; supposing 

 an atom of oxygen to be 1 f." It is really too much for the 

 Doctor to commit such errors, and then transfer them to that 

 accurate philosopher. To make the blunder more comical, he 

 quotes the experiment in a note to the same page, from which it 

 appears, that the atom of fluoric acid, on the Doctor's own 



* Spstortjl. p. liS9. t Ibid. I. p. 19». 



