_B._ No; but I ascribe it to the like motion in the sun and moon. For such motions meeting, must needs cast the stream of the air towards the poles; and then there will be the same necessity for the descent there, that there is in other places, though perhaps a little more slowly. For you may have observed, that when it snows in the south parts, the flakes of snow are not so great as in the north: which is a probable sign they fall in the south from a greater height, and consequently disperse themselves more, as water does that falls down from a high and steep rock. _A._ It is not improbable. _B._ In natural causes all you are to expect, is but probability; which is better yet, than making gravity the cause, when the cause of gravity is that which you desire to know; and better than saying the earth draws it, when the question is, how it draws. _A._ Why does the earth cast off air more easily than it does water, or any other heavy bodies? _B._ It is indeed the earth that casteth off that air which is next unto it; but it is that air which casteth off the next air; and so continually, air moveth air; which it can more easily do than any other thing, because like bodies are more susceptible of one another’s motions: as you may see in two lute-strings equally strained, what motion one string being stricken communicates to the air, the same will the other receive from the air; but strained to a differing note, will be less or not at all moved. For there is no body but air, that hath not some internal, though invisible, motion of its parts: and it is that internal motion which distinguisheth all natural bodies one from another. _A._ What is the cause why certain squibs, though their substance be either wood or other heavy matter, made hollow and filled with gunpowder, which is also heavy; do nevertheless, when the gunpowder is kindled, fly upwards? _B._ The same that keeps a man that swims from sinking, though he be heavier than so much water. He keeps himself up, and goes forward, by beating back the water with his feet; and so does a squib, by beating down the air with the stream of fired gunpowder, that proceeding from its tail makes it recoil. _A._ Why does any brass or iron vessel, if it be hollow, float upon the water, being so very heavy? _B._ Because the vessel and the air in it, taken as one body, is more easily cast off than a body of water equal to it. _A._ How comes it to pass, that a fish, (especially such a broad fish as a turbot or a plaice, which are broad and thin), in the bottom of the sea, perhaps a mile deep, is not pressed to death with the weight of water that lies upon the back of it? _B._ Because all heavy bodies descend towards one point, which is the centre of the earth: and consequently the whole sea, descending at once, does arch itself so, as that the upper parts cannot press the parts next below them.