EXPANSIBILITY. 265 



lead undergo any change whatever; on the 

 contrary, the air within the bladder dilates and 

 expands to its utmost extent. 



What is the extent to which air may expand, 

 with what velocity it may move, and what 

 resistance it is able to overcome, must necessa- 

 rily be very difficult to ascertain. Mr BOYLE 

 was of opinion, that air was capable of expand- 

 ing in the proportion from 1 to 1000 times. Sir 

 ISAAC NEWTON considered this property of air 

 to be almost unlimited and unbounded ; that it 

 extended, perhaps, to one million times more 

 than its original bulk ; that is to say, that one 

 cubic foot of air, at its initial state, was capable 

 of dilating and filling the whole space of one 

 million cubic feet in extent. Dr. GREGORY, in 

 his astronomy, mentions an opinion, which he 

 probably derived from Newton ; that if a cubic 

 foot of air were removed to the elevation of one 

 semi-diameter above the surface of the earth, 

 that it would expand and extend as far as the 

 orb of the planet Saturn. It is not my present 

 intention to examine the accuracy of these opi- 

 nions, or attempt to reconcile the difference 

 which exists between them. However discor- 

 dant they may appear in point of quantity, they 

 agree in matter of fact, and tend to establish the 

 wonderful power of expanding which air essen- 

 tially contains. 



The late ingenious Mr. SMEATON has pub- 



