L203 
CLASS 
III. 
INFLAMMABLE SUBSTANCES. 
THE third chals of the objeds of chemistry, in the plan which I 
have adopted, is that of the INFLAMMABLE Or COMBUSTIBLE 
SUBSTANCES. 
By the inflammation of a body, is meant a rapid destruction and 
change, which it fuffers when exposed to the action of heat and air at 
the ſame time ; which change is attended with the emission of a great 
quantity of heat and light, and ends in a total lofs or privation of the 
quality of inflammability. 
When the general effects of heat were formerly explained to you, 
some notice was taken of the phenomena of inflammation, and of the 
general nature of this class of bodies. And the opinions which for 
merly prevailed, as well as thoſe which now prevail concerning the 
nature of it, were briefly stated, and have since been more fully ex 
plained to you occasionally. 
The opinion that is now the moſt generally approved, had its rise 
from the numerous investigations and experiments that have been made 
since the laſt twenty or thirty years on the nature and properties of 
the different elaſtic fluids which are found in nature, or may be pro 
duced by art. 
Cea