114 British Association for the Advancement of Science. 



mode of conception was arbitrary, and the argument founded 

 upon it, baseless ; for if we investigate the relation between the 

 height of any point in the atmosphere, and the density of the air 

 at that point, on the supposition that the compressing force is as 

 the Mth power of the density, we find that the density vanishes 

 at a finite height whenever n is greater than unity. Therefore, 

 though the atmosphere do not consist of indivisible particles, it 

 will still have a finite surface. In fact, the finite surface of the 

 atmosphere no more proves the atomic constitution of air, than 

 the finite surface of water, in a vessel, proves the atomic constitu- 

 tion of water. 



Section B. Chemistry and Mineralogy. 



Prof. Graham, President of the Section, opened the meeting 

 with some observations on the recent progress of chemistry, 

 which, in his view, is advancing with unprecedented rapidity, 

 both in its theory and its applications. The organic department 

 is the most productive, and at present engrosses the attention of 

 chemists. In this department he would allude to what seemed 

 to him its two great features. 1. The happy generalization of 

 Dumas, — the law of substitutions, which had been the clue to so 

 many discoveries. He first applied it to the action of chlorine 

 upon organic compounds, finding that when chlorine acts upon 

 those bodies, for every atom of hydrogen abstracted in the form 

 of hydrochloric acid, an atom of chlorine is left in its place. The 

 same doctrine has been successfully applied to the action of oxy- 

 gen and other elements on the same bodies. Thus, in the oxi- 

 dation of alcohol in the acetous fermentation, hydrogen is with- 

 drawn in the form of water, by combining with oxygen, and at 

 the same time the hydrogen is replaced by an exactly equivalent 

 quantity of oxygen. The same law led M. Dumas to his most 

 recent discovery, that of chloro-acetic acid, — an acetic acid, in 

 which chlorine is substituted for oxygen. One of the most in- 

 teresting applications of this doctrine is that by M. Regnault, in 

 elucidating the history of the chlorides of carbon. For the orig- 

 inal discovery of these compounds we are indebted to Mr. Fara- 

 day. One of them which contains its two elements in the ratio 

 of single equivalents has been named the protochloride of carbon. 

 What is its real nature ? M. Regnault has traced it through va- 

 rious compounds, all produced by the action of chlorine on ole- 



