CHAP. III. 



OF THE SPECIFIC GRAVITIES OF OXYGEN 

 AND HYDROGEN GASES. 



IT is only of late years, that the great impor- 

 tance of an accurate knowledge of the specific 

 gravities of the gases has been fully appreciated. 

 Three different sets of experiments on the sub- 



J ments al- 



ject have been laid before the public. The first ready made 

 was by JBiot and Arago, which was published in mine these 

 the Memoir -es de V Institute, for 1806, p. 320. gravities ' 

 They give a table of the specific gravity of a 

 few of the most important gases, and describe 

 the processes by which they were determined. 

 The next was a paper inserted by me in the 

 16th volume of the Annals of Philosophy. It 

 contained the specific gravities of 23 gases. 

 The experiments were made with every precau- 

 tion which I could think of, to secure me 

 against mistakes ; and I believe them to come 

 as near the truth as we can reach, with our pre- 

 sent means of operating. The third set was 

 by Messrs. Berzelius and Dulong, and published 

 in the Annales de Chimie et de Physique^ for 

 1820.* They determined the specific gravity of 

 oxygen, hydrogen, carbonic acid, and azotic 



* Vol. XVI. p. 386. 

 Vot. I. D 



