CHAPTER XT. 



OK THE INEQUALITY OF PRESSURE IN THE 



AIR, IN CONSEQUENCE OF INEQUALITY OF 



EXTERNAL RESISTANCE, 



HOPING that the facts which I have advanced, 

 are sufficient and conclusive ; not only to prove 

 the expansive power of air, independently of 

 external influence ; and that the pressure which 

 it produces on surrounding bodies, is to be 

 referred to expansibility, not to density and 

 weight; I shall now proceed to detail the 

 effects which are produced by the air, when 

 there exists an inequality of resistance in the 

 medium by which it is surrounded. 



Whenever the substraction of external re- 

 sistance takes place, from any one part, the 

 expansible force of the air becomes immedi- 

 ately dilated, and directed to the particular 

 situation where the least resistance exists; a 

 change of pressure, consequently, takes place, 



