VOL. LV.J PHILOSOPHICAL TRANSACTIONS. 2^5 



from the lungs as when we breathe in cold air, yet that moisture is not so 

 visible. !» 



Water being extremely heated, i. e. to the degree of boiling, its particles, in 

 quitting it, so repel each other, as to take up vastly more space than before, and 

 by that repellency support themselves, expelling the air from the space they oc- 

 cupy. That degree of heat being lessened, they again mutually attract, and 

 having no air-particles mixed, to adhere to, by which they might be sujjported 

 and kept at a distance, they instantly fall, coalesce, and become water again., 

 The water commonly diffused in our atmosphere never receives such a degree of 

 heat from the sun, or other cause, as water has when boiling; it is not, there- 

 fore, supported by such heat, but by adhering to air. Water being dissolved 

 and adhering to air, that air will not readily take up oil, because of the natural 

 repellency between water and oil. Hence cold oils evaporate but slowly, the air 

 having generally a quantity of dissolved water. Oil being heated extremely, the 

 air that approaches its surfape will be also heated extremely; the water then quit-* 

 ing it, it will attract and carry off" oil, which can now adhere to it. Hence the 

 quick evaporation of oil heated to a great degree. Oil being dissolved in air, the 

 particles to which it adheres will not take up water. Hence the suffocating na- 

 ture of air impregnated with burnt grease, as from snuffs of candles, and the 

 like. A certain quantity of moisture should be every moment discharged and 

 taken away from the lungs. Air that has been frequently breathed is already 

 overloaded, and for that reason can take no more, so will not answer the end. 

 Greasy air refuses to touch it. In both cases suffocation ensues for want of 

 the discharge. 



Air will attract and support many other substances. A particle of air loaded 

 with adhering water, or any other matter, is heavier than before, and would de- 

 scend. The atmosphere supposed at rest, a loaded descending particle must act 

 with a force on the particles it passes between, or meets with;, sufficient to over- 

 come in some degree their mutual repellency, and push them nearer to each 

 A other. Thus, supposmg the particles abcd, and the others 



o o o near them to be at the distance caused by their mutual repel- 



Fo BO CO GO lency (confined by their common gravity) if a would descend 

 o DO o to E, it must pass between b and c. When it comes be- 



o o o o tween b and c, it will be nearer to them than before, and 

 E must either have pushed them nearer to f and g, contrary 



to their mutual repellency, or pass through by a force exceeding its repellency 

 with them. It then approaches d, and, to move it out of the way, must act 

 on it with a force sufficient to overcome its repellency with the two next lower 

 particles, by which it is kept in its present situation. Every particle of air, there- 



VOL. XII. Gg 



