472 
Dr. Ure on the ultimate analysis of 
Cannel coal from Woodhall, near Glasgow, specific gra- 
vity 1.228, resembles a compound of 
Carbon 9 atoms . . 6.750 . . 73.9 
Hydrogen 3 . . 0.375 . . 4.2 
Oxygen 2 . . 2.000 . . 21.9 
9.125 100.0 
In both of these bodies there is an excess of carbon beyond 
the 3 atoms of olefiant gas and 2 of carbonic oxide. The for- 
mer coal has 2 extra atoms of carbon, and the latter 4 atoms. 
Hence, this coal is found at the Glasgow gas works to yield 
a very rich burning gas. I do not know whether the azote be 
essential to the constitution of this coal, or accidentally in- 
troduced from animal remains at the formation of the strata. 
The elements of indigo may be grouped as follows : 
Carbon 16 atoms . . 12.0 . . 72.70 
Hydrogen 6 . . 0.75 . . 4.55 
Oxygen 2 . . . 2.00 . . 12.15 
Azote . 1 . . . 1.75 . . 10.60 
16.50 100 00 
or, in other terms, we shall have 
1 atom cyanogen, 6 atoms olefiant gas, 2 atoms carbonic 
oxide, and 6 atoms of carbon in excess. 
I had intended to pursue, at considerable detail, my re- 
searches on this curious azotized product of vegetation, but 
the subject having been lately taken up, and ingeniously pro- 
secuted by my pupil and friend, Mr. Walter Crum, I was 
induced to leave it in his hands. He announced to me the 
presence of hydrogen in indigo, before I had analyzed this 
substance myself ; and drew my attention, particularly, to 
