CARBON. 153 



while the same volume of it is burning. This 

 vapour, then, if we could get rid of the smell, 

 would be the best substance for giving light ; 

 one obvious method would be, to take care that 

 the whole of it is consumed, and that none es- 

 capes under the form of naphtha vapour. 



2. Carburetted hydrogen gas can only be ob- 

 tained pure, by stirring the mud at the bottom gen 

 of stagnant waters, during hot weather. It was 

 first accurately examined by Mr. Dalton. Soon 

 afterwards, I published a set of experiments on 

 it, in the first volume of the Wernerian Memoirs. 

 I took its specific gravity at two different times, 

 with great care. Gas, collected at Restalrig, 

 near Edinburgh, had the specific gravity of 

 0*5554. The mean of the specific gravity of 

 three specimens, collected in the neighbourhood 

 of Glasgow, was 0*5576. It will be proper to 

 state each of these trials, as the gas was collected 

 at three different times. 



1st trial 0-5602 

 2d trial 0-5558 

 3d trial 0-5570 



It is obvious that the gas was not of equal purity 

 in each of these trials ; it was purest in the se- 

 cond specimen, the specific gravity of which 

 comes nearest that of my former experiments. 

 The mean of the two gives us 0*5556, which is 

 undoubtedly very near the truth. Berzelius and 

 Dulong state the specific gravity of this gas to 



