202 PROPERTIES OF AIR ' 



of apparent gravity as much the power ojr 

 pressing bodies upwards as downwards, of 

 ascending into the nostrils, as descending into 

 the lungs ; that a small portion of air, sepa- 

 rated by the thinnest covering possible, from a 

 larger column, suffers no additional pressure ; 

 that the back of my hand sustains no more 

 pressure from the large column above, than the 

 palm from the small portion of air below it; 

 that we feel no weight that we suffer no vio- 

 lence that we are exposed to no danger : 

 that, in fact, the equable pressure of the air, 

 in every direction, under the same circum- 

 stances of external influence, is no more capa- 

 ble of smashing our bodies to a cake, than it is 

 of bursting the parietes, or sides, of the thin- 

 nest air-bubble that can be conceived.* 1 



* I might produce, without end, facts to prove this par- 

 ticular attribute. The expansible power of air in every direc- 

 tion is further proved, by putting a piece of lead to the 

 mouth of a syringe, and abstracting the air out of it ; the ex- 

 pansible force of the external air, is found capable of keeping 

 the lead in forcible contact with the mouth of the syringe, in 

 whatever direction the weight may be situated. It is the case 

 with two hemispheres, when the air has been exhausted out 

 of them, &c. It is the case with a bladder placed upon an 

 exhausted receiver : it will burst with as much facility down- 

 wards, sideways, and upwards, &c. 



