354 Afr. smeaton’s Fundamental Experiments , &c. 
above fhewn, will acquire an increafe of velocity by their ftroke 
upon each other. 
In a like manner the idea of a perpetual motion , perhaps, at 
firft fight, may not appear to involve a contradiction in terms 
but we fhall be obliged to confefs that it does, when, on exa- 
mining its requisites for execution, we find we fhall want bo- 
dies having the following properties ; that when they are made 
to a fiend again ft gravitation their abfolute weight fhall be lefs ; 
and that when they defiend by gravitation (through an equal 
Space) their abfolute weight fhall be greater; which, according 
$o all we know of nature, is a repugnant or contradictory idea * 
