132 PROCEEDINGS OF THE SCIENTIFIC ASSOCIATION. 
paring its percentage composition with that of the best 
specimen reported on by Sir R. I. Murchison, namely, the 
sample numbered 18, from Point Noir ( Geolog . Bep. Trini- 
dad). But to compare the composition of different speci- 
mens of coal, the adventitious and variable constituents, 
water, sulphur and ash, should be eliminated ; then the 
relative proportions of the essential elements, carbon, hydro- 
gen, oxygen and nitrogen, correctly represent the degree of 
carbonization. Regarded in this manner the Montserrat 
specimen compares favourably with that from Point Noir, as 
the following numbers show. 
100 parts of true coal, exclusive of water, sulphur and 
ash, contain : 
Carbon . . . 
Hydrogen 
Oxygen ... 
Nitrogen 
Montserrat. Point Noir. 
78-743 77-16 
6-258 5-95 
12 ' 128 i 16-89 
2-871 ) 
On the other hand, the Montserrat coal, according to the 
specimen received, contains too large a proportion of sulphur 
as pyrites. 
The presence of much sulphur not only depreciates the 
value of coal as fuel but becomes highly objectionable when 
the coal is applied to gas-making, as it results in the gas 
becoming largely contaminated with sulphur compounds. 
The latter, being burnt with the gas, generate sulphur 
dioxide, which not only vitiates the atmosphere but is con- 
verted into sulphuric acid, and condensing on books, 
pictures, etc., rapidly destroys them. 
It is more than probable, however, that the thorough 
ventilation insured in West Indian buildings would render 
