of a homogeneous fluid mass that revolves upon an axis. 1 05 
upon every point of the surface H K I. The whole mass of 
fluid, NOL, will therefore be in equilibrio, if it be urged by 
no other forces. But the attraction of the stratum upon all 
the matter within it, is a new force brought into play, the 
efforts of which must be balanced, otherwise the equilibrium 
could not subsist. Now this new force is distinct from the 
pressure caused by the gravity, and can never be included in 
it. Two separate principles must therefore be employed to 
ensure the equilibrium of the fluid body HKI, when acted 
upon by the two independent forces. But a fluid body can- 
not be in equilibrio by the action of external forces upon it, 
except in one of these two ways : either there must be an 
equable pressure upon the outer surface ; or, all the forces 
that act upon every separate particle must destroy one ano- 
ther. We are therefore necessarily led to suppose, that the 
added stratum must possess such a figure as to attract every 
particle in the inside with equal force in all opposite direc- 
tions. By the help of this principle, and by no other means, 
the fluid body HKI, will still continue to be in equilibrio 
when subjected to the additional pressure, and to the new 
attractive force. 
When more strata are added, they must separately possess 
the property of attracting every particle in the inside with 
equal force in opposite directions ; by which supposition, we 
are brought at every step to the same circumstances, as in 
the case when there is no attraction between the particles. 
The whole fluid mass being ultimately divided into level 
strata, the property common to each must belong to the 
aggregate of any number of them . 
On the whole, it is not sufficient for the equilibrium of a 
mdcccxxiv. P 
