74 ESSAYS ann OBSERVATIONS 
ftance and a little fubftance are moved 
by it, or when a great velocity and a lit- 
tle velocity are imparted to the fame fub- 
ftance? When we-endeavour to communi- 
cate motion to fuch a fubftance, we muft be 
confcious of fome kind of feeling ; and thefe 
feelings moft be different in different cafes. 
Thus the idea of refiflance, as it called, to 
motion, in the moft inactive fubftance we 
can imagine, would be fuggefted tous from 
thefe perceptions; and is precifely the fame 
with what we experience daily in handling 
of matter. Nor does it feem poflible to con- 
ceive an extended, impenetrable fubftance, 
divefted of this kind of refiftance from iner- 
tia. The larger the fubftance is which we 
intend to move with agiven velocity, the 
greater force muft be applied: and, could we 
fuppofe it actually infinite, no finite force 
could move it at all. 
THERE is avery extraordinary paflagein 
Mr. M‘claurin’s Account of Sir Ifaac Newton's 
Philofophy. P. 100. which, in refpe& of the 
high merit of the author, deferves our at. 
tention. It is there faid, ‘ That, for ought 
** we know, matter may be of kinds fo dif- 
ferent from each other, that the folid ele- 
mentary 
