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 occupy. That degree of heat being lessened, they again mutually attract, and having no air-particles mixed to adhere to, by which they might be supported 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, therefore, supported by such heat, but by adhering to air.
Water being dissolved in, and adhering to air, that air will not readily take up oil, because of the mutual 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 surface will be also heated extremely; the water then quitting 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 nature 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 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 descend.
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 overcome, in some degree, their mutual repellency, and push them nearer to each other.