36 ESSAYS anv OBSERVATIONS 
Sir T/aac’s firftinftance, of a man’s prefling 
a ftone with his hand; we muft. diftinguith 
betwixt a moveable and immoveable obftacle. 
If aman prefs an immoveable obftacle with 
his hand, I cannot here difcover any thing 
but mere refiftance, which is not to be over- 
come by the force of the hand. This is an 
effec which muft follow from the impene- 
trability of matter, without neceffity of ta+ 
king under confideration, any other of its pro- 
perties. I difcover here no reaction. There 
is no counter-action or impulfe in the ftone, 
to correfpond to the action or impulfe of the 
hand. There is nothing but refiftance, which 
is indeed an action, but an action which 
is not exerted upon the hand: the action is 
exerted within the refifting body itfelf, to 
preferve it from motion. And, if this refift- 
ance fhall be conceived as a counter-action, 
which it may be in a loofe way of thinking; 
T cannot however conceive any equality be- 
twixt the prffure of my hand and this fup- 
pofed counter-aétion of the ftone. At this 
rate, the counter-action of the ftone is equal 
to every degree of imprefled force, provided 
the impreffed force be not great enough to 
move the ftone ; and fo it will be equal at 
the — 
