SIMPLE COMBUSTIBLES. 19 
SIMPLE COMBUSTIBLES. 
44. By this term we are to understand all those mi- 
neral substances, capable of combustion, which have not 
been discovered to consist of more than a single com- 
ponent part. They are four in number ; hydrogen, sul* 
phur, phosphorus^ and carbon. 
45. Hydrogen, as its name imports, is a principal con- 
stituent part of water ; for, singular as it may appear, 
that well-known fluid is formed by a combination of two 
species of air or gas, called hydrogen and oxygen (21), 
and in the proportion of about fifteen parts of the for- 
mer and eighty-five parts of the latter. This gas had 
formerly the denomination of inflammable air, and has 
long been known in mines under the name of fire-damp. 
It is about twelve times lighter than atmospheric air. 
When pure it soon destroys such animals, and ex- 
tinguishes all such flaming substances, as are immersed 
in it. Mixed with atmospheric air, it explodes with 
great violence on the application of any ignited body. 
46. Sulphur is a simple combustible substance, of 
yellow colour, which is found pure, or native, in several 
parts of the world, and is sufficiently familiar to us 
under the name of brimstone (21 1 ). It strongly attracts 
oxygen (21 ), and is thereby converted into sulphuric 
acid (24). It frequently occurs in combination with 
mineral substances, such as arsenic, antimony, copper, 
and other metallic ores. 
47. Phosphorus is a combustible substance which, 
when pure, somewhat resembles bees'-wax both in co- 
lour and consistence ; and, when exposed to the air 
under the usual temperature of our atmosphere, is lu- 
minous in the dark, and has a smell somewhat resem- 
