. 
: 
4 
q , 
‘PHYSICALaxn LITERARY. 23 
ance. They are fimple ideas, and therefore 
incapable of a definition ; but their difference 
willbe obvious, by confidering a man in the 
act of pufhing againft an obftacle, and bare- 
ly refifting force applied againft him, without 
pufhing again, or counteracting. The man, 
no doubt, is active in refifting, as well as in 
pufhing ; but the actions are very different in 
their nature, and carefully to be diftinguifhed 
in accurate reafoning. Ina word, the ten- 
dency of impulfe is, to produce motion ; the 
tendency of refiftance is, to prevent it. Thefe 
powers, therefore, fo oppofite to each other, 
fhall hereafter be diftinguifhed by different 
names. The vis infita fhall be appropriated 
to that power which is favourable to motion ; 
leaving the other power which refifts motion 
to be denominated by the vzs inertia, or ra- 
ther vis refiftentia. 
Tuo’ this vs zmertie be a power, as obfer- 
ved, inherent in all matter, there are certain 
experiments which may appear to clafh with 
it, and which, upon that account, merit at- 
tention. Ifa round ball be laid upon a ho- 
rizontal table za vacuo, in which fituation 
there will be no counteraétion of gravity, it is 
certain, that the {moother the ball and table 
are, 
