OF THE EQUILIBRIUM OF A SYSTEM. 173 



?ilways equal, and directed contrary ways." He proceeds, 

 " if any body draws or presses another, it is itself as much 

 drawn or pressed. If any one presses a stone with his 

 finger, his finger is also pressed by the stone. If a horse 

 is drawing a weight tied to a rope, the horse is also equally 

 drawn backwards towards the weight ; for the rope, being 

 distended throughout its length, will, in the same en- 

 deavour to contract, urge the horse towards the weight, 

 and the weight towards the horse, and will impede the pro- 

 gress of the one as much as it promotes the advance of 

 the other." Now, although Newton has always applied 

 this law in tlie most unexceptionable manner, yet it must 

 be confessed that the illustrations here quoted are clothed 

 in such language as to have too much the appearance of 

 paradox* When we say that a thing presses another, we 

 commonly mean, that the thing pressing has a tendency to 

 move forwards into the place of the thing pressed : but the 

 stone would not sensibly advance into the place of the 

 finger, if it were removed ; and in the same manner we 

 understand, that a thing pulling another has a tendency 

 to recede further from the thing pulled, and to draw this 

 after it : but it is obvious that the weight, which the horse 

 is drawing, would not return towards its first situation, 

 with the horse in its train, although the exertion of the 

 horse should entirely cease ; in these senses, therefore, we 

 cannot say, that the stone presses, or that the weight 

 pulls ; and we have no reason to offend the natural pre- 

 judices of a beginner, by introducing paradoxical expres- 

 sions without necessity. Yet it is true in both cases, that 

 if all friction, and all connexion with the surrounding 

 bodies, could be instantaneously destroyed, the point of 

 the finger and the stone would recede from each other, 



