_ actions of two bodies upon each other, are 
PHYSICAL ann LITERARY. 33 
Or ACTION ann REACTION. 
JT is laid down as an univerfal law of mat- 
- ter, “ that reaction is always contrary 
*« and equal to action.”’ Or, “that the mutual 
*« always equal, and with oppofite directions.” 
And Sir Ifaac Newson, in illuftrating: this 
law, gives particular inftances of its taking 
place in all the different actions of matter ; 
to wit, in impulfe, in preffure, and in refift- 
ance. For my part, I have always been 
puzled about this law, and am uncertain, 
after all, whether I have a juft conception 
of it. Are we tounderftand it to be a pro- 
perty of matter in general, that when acted 
upon, it exerts an equal and contrary action ? 
Or only, that in thefe particular cafes where 
matter reacts, the reaction is always equal and 
contrary to the aétion? The former is Sir I 
_ Saac’s fenfe of this law; which is evident, 
_ from his placing it among the laws that go- 
_ vern all’ matter'in' general; as well as from 
‘ E his 
ty 
