56 
Steam Engine, 
laws. It is of importance to understand diat the descent 
of falling bodies is the same every where on the surface of 
the earth ; but from that and some other particular facts 
to infer the law of gravitation, or that all matter attracts 
with a force decreasing as the square of the distance, is a 
much higher attainment in science. In the train of ex- 
periments lately engaging my attention some new facts 
have been ascertained, which, with others, seem to author- 
ise the deduction of general laws, and such as will have 
influence in various departments of natural philosophy and 
chemistry. 
As the detail of experiments will be best understood 
and their application seen, if the laws of principles alluded 
to be kept in view, it may be proper here to state them ; 
though it must not be understood that they were proceed- 
ed upon hypothetically in the direction of those experi- 
ments. On the contrary, the first law, which is as a mir- 
ror in which all the experiments are best viewed, was last 
detected, and after all the particular facts had been previ- 
ously ascertained. 
1. When two elastic fluids, denoted by and are. 
mixed together, there is no mutual repulsion amongst 
their particles ; that is, the particles of A do not repel those 
of B^ as they do one another. Consequently, the pres- 
sure or whole weight upon any one particle arises solely 
from those of its own kind. 
2. The force of steam from all liquids is the same, at 
equal distances above or below the several temperatures at 
which they boil in the open air : and that force is the same 
under any pressure of another elastic fluid as it is in va - 
cuo. Thus, the force of aqueous vapour of 212° is equal 
to 30 inches of mercury ; at 30° below, or 182°, it is of 
half that force ; and at 40° above, or 252°, it is of double 
the force ; so likewise the vapour from sulphuric ether 
which boils at 102°, then supporting 30 inches of mercu- 
