Professor Thomas Thomson. 95 



Principles of Chemistry by Experiment," in two volumes. 

 It contained "the result of many thousand experiments, 

 conducted with as much care and precision as it was in his 

 power to employ." In this work he gives the specific gra- 

 vities of all the important gases, ascertained by careful ex- 

 periment. In these researches he had associated with him 

 Mr Alexander Harvey as his assistant, a gentleman pos- 

 sessed of high mechanical and intellectual talents, who has 

 since risen to eminence as a valuable citizen and magistrate 

 of his adopted city. The data thus ascertained were often 

 disputed and attacked in strong but unphilosophical terms, 

 as they tended to supersede previous experimental deduc- 

 tions ; but the excellent subsequent determinations of spe- 

 cific gravities by Dumas, which were made at the request of 

 Dr Thomson, after that distinguished chemist had visited 

 him at Glasgow in 1840, fully substantiated the greater ac- 

 curacy of Dr Thomson's numbers over those which preceded 

 him, and in most cases furnished an identity of result. The 

 atomic numbers given in his " First Principles" as the result 

 of his labours, were the means of a vast number of experi- 

 ments made by himself and pupils, the data of which still 

 exist in his series of note-books. They all tended to the re- 

 sult that the atomic weights of bodies are multiples by a 

 whole number of the atomic weight of hydrogen, a canon 

 confirmed to a great extent by the recent experiments of 

 French and German chemists, and which he himself was the 

 first to point out in the case of phosphorus. That the author 

 of our memoir was frequently in error in his experiments is 

 not attempted to be denied ; for, as the great Liebig has 

 said, it is only the sluggard in chemistry who commits no 

 faults ; but all his atomic weights of important bodies have 

 been confirmed. After the publication of this work, he de- 

 voted himself to the examination of the inorganic kingdom 

 of nature, purchasing and collecting every species of mineral 

 obtainable, until his museum, which he has left behind him, 

 became not only one of the noblest mineral collections in the 

 kingdom, but a substantial monument of his taste and of his 

 devotion to science. The results of his investigation of mi- 

 nerals were published in 1836, in his " Outlines of Mine- 



