CARBON. 155 



In the case of carbon vapour and hydro- 

 gen gas, we may substitute atoms for volumes. 

 It is obvious, therefore, that this gas is a com- 

 pound of 1 atom carbon, and 2 atoms hydrogen. 

 And as an atom carbon weighs O75, and an 

 atom of hydrogen O1&5, the atomic weight of 

 this substance is unity, or the same as oxygen. 

 Its specific gravity is only half that of oxygen 

 gas ; because, a volume of oxygen gas is equiva- 

 lent to two atoms, while a volume of this gas is 

 equivalent only to one atom. 



3. There exists a third combination of carbon Naphtha- 

 and hydrogen, which has come to our knowledge quic'arbu- 

 since coal gas was employed for lighting tbedrogeo. 7 ' 

 streets. It was first noticed by Mr. Garden, 

 who described some of its most remarkable pro- 

 perties, in the year 1820.* Soon after, I got 

 from Mr. Cooper a considerable quantity of this 

 substance, which I purified by sublimation, and 

 subjected to a chemical examination. A valua- 

 ble set of experiments on this substance was made 

 by Dr. Kid, and published in the Philosophical 

 Transactions for 1821 ; he gave it the name of 

 Naphthaline. I have only to refer the reader to 

 this interesting paper for a satisfactory explana- 

 tion of the formation and properties of this sin- 

 gular substance. But, as Dr. Kid made no ex- 

 periments to determine its constituents, it may 



* Annals of Philosophy, XV. 1.7. 



