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fame Jlate of elaficity ; that is, in which the abfo- 
Jute force of elafticity, under all the different de- 
grees of preffure, is conftantly the fame. (The 
abfolute force of elafticity is meafured by the force 
exerted between two particles of given magnitudes 
and figures, at a given diftance.) But there is 
no reafon, from any experiments, to conclude, 
that the denfity of the air will be fimply as 
the comprefling force, in different abfolute forces of 
elafticity. On the contrary, fince the proportion 
of the compreffing forces is found to obtain, be- 
tween the denfities, when the abfolute elafticity is 
conftant ; this alone is a proof, that the like pro- 
portion will not obtain, if the abfolute elafticity be 
changed as well as the compreflive force. 
Imagine two parcels, fimilarly fhaped, A and B, 
of different fluids, the fame in all their other pro- 
perties, and fimilarly, but unequally,, elaftic; that 
is, imagine the integrant particles of A to be equal 
in quantity of matter and bulk, and fimilar in figure, 
to the integrant particles of B, feverally ; and if 
each of the integrant particles of A, be itfelf an 
aggregate of leffer integrants, each of the integrant 
particles of B is to be underftood to be a like aggre- 
gate of equal and fimilar leffer integrants, fimilarly 
compofed ; and whatever forces, except that of 
elafticity, are exerted between the particles of A, 
imagine equal forces, of the fame kinds, exerted 
according to the fame laws, between the particles 
of B. Likewife, imagine the equal and fimilar 
particles to be fimilarly fituated, in their refpeftive 
mafles. Such fluids are the fame in all refpedts, 
elafticity excepted. Further, imagine an elaftic 
force to be exerted between every two integrant 
particles 
