192 Newton's Letters^ Hypothesis and Experiments 



the slow ascent of so much matter out of the bowels of the 

 earth in an aerial form, which for a time constitutes the at- 

 mosphere, but being continually buoyed up by the new air, ex- 

 halations, and vapours rising underneath, at length (some part 

 of the vapours which return in rain excepted) vanishes again 

 into the aetherial spaces, and there perhaps in time relents 

 and is attenuated into its first principle. For nature is a per- 

 petual circulatory worker, generating fluids out of solids, and 

 solids out of fluids, fixed things out of volatile, and volatile 

 out of fixed, subtile out of gross, and gross out of subtile, 

 some things to ascend and make the upper terrestrial juices, 

 rivers, and the atmosphere, and by consequence others to de- 

 scend for a requital to the former. And as the earth, so 

 perhaps may the sun imbibe this spirit copiously, to conserve 

 his shining, and keep the planets from receding further from 

 him : and they that will may also suppose that this spirit 

 affords or carries with it thither the solary fuel and material 

 principle of light, and that the vast aetherial spaces between 

 us and the stars are for a sufficient repository for this food of 

 the sun and planets. But this of the constitution of aetherial 

 natures by the bye. 



In the second place, it is to be supposed that the aether is a 

 vibrating medium like air, only the vibrations far more swift 

 and minute ; those of air made by a man's ordinary voice, suc- 

 ceeding one another at more than half a foot or a foot di- 

 stance, but those of aether at a less distance than the hundred- 

 thousandth of an inch. And as in air the vibrations are some 

 larger than others, but yet all equally swift (for in a ring of 

 bells the sound of every tone is heard at two or three miles 

 distance in the same order that the bells are struck), so I sup- 

 pose the aetherial vibrations differ in bigness, but not in swift- 

 ness. Now these vibrations, besides their use in reflexion and 

 refraction, may be supposed the chief means by which the 

 parts of fermenting and putrifying substances, fluid liquors, 

 or melted, burning, or other hot bodies, continue in motion, 

 are shaken asunder like a ship by waves, and dissipated into 

 vapours, exhalations, or smoke, and light loosed or excited in 

 those bodies, and consequently by which a body becomes a 

 burning coal, and smoke flame; and I suppose flame is no- 

 thing but the particles of smoke turned by the access of light 

 and heat to burning coals, little and innumerable. 



Thirdly, the air can pervade the bores of small glass pipes, 

 but yet not so easily as if they were wider, and therefore 

 stands at a greater degree of rarity than in the free aerial 

 spaces, and at so much greater a degree of rarity as the pipe 

 is smaller, as is known by the rising of water in such pipes to 



