Atmosphere. 98 



doubtedly be crushed in a moment, if all 

 parts of our bodies were not filled either 

 with air or some other ela&tic fluid, the 

 spring of which is just sufficient to coun- 

 terbalance the weight of the atmosphere,, 

 But, whatever this fluid may be, it is cer- 

 tain that it is just able to counteract the 

 weight of the atmosphere, and no more : 

 for if any considerable pressure be super- 

 added to that of the air, as by going into 

 deep water ,or the like,it is always severe- 

 ly felt, let it be ever so equable, at least 

 when the change is made suddenly ; and 

 if, on the other hand, the pressure of the 

 atmosphere be taken off from any part of 

 the human body, as the hand for instance, 

 when put over an open receiver, from 

 whence the air is afterwards extracted, 

 the weight of the external atmosphere 

 then prevails, and we imagine the hand 

 strongly sucked down into the glass. 



The difference in the weight of the air 

 which our bodies sustain at one time 

 more than another, is also very consider- 

 able, from the natural changes in the state 

 of the atmosphere. This change takes 

 place chiefly in countries at some distance 

 from the equator ; and, as the barometer 



