PHTSICAL AND LITERARY. 37 



!0f action and reaction. 



IT is laid down as an univerfal law of 

 matter, " that rea(5lion is always con- 

 f trary and eqv^al to adlion." Or, " that 

 .*' the mutual adtions of two bodies upon 

 '• each other, are always equal, and with 

 f oppofite diredions." And Sir Ifaac 

 Newton, in iUuftrating this law, gives 

 particular inftances of its taking place in- 

 all the different adtions of matter ; to wit, 

 in impulfe, in prefTure, and in refiftance. 

 For my part, I have always been puzzled 

 about this law, and am uncertain, after 

 all, whether I have a juft conception of 

 it. Are we to underftand it to be a pro- 

 perty of matter in general, that when adl- 

 ed upon, it exerts an equal and contrary 

 adion? Or only, that in thefe particular 

 cafes where matter reads, the readion is 

 always equal and contrary to the adion ? 



The 



