_B._ I showed you yesterday, in discoursing of rain, how by this compounded motion of the sun’s body, the air was every way at once thrust off west and east; so that where it was contiguous, the small parts of the water were forced to rise, for the avoiding of vacuum. Think then that your hand were in the place of water so exposed to the sun. Must not the sun work upon it as it did upon the water? Though it break not the skin, yet it will give to the inner fluids and looser parts of your hand, an endeavour to get forth, which will extend the skin, and in some climates fetch up the blood, and in time make the skin black. The fire also will do the same to them that often sit with their naked skins too near it. Nay, one may sit so near, without touching it, as it shall blister or break the skin, and fetch up both spirits and blood mixt into a putrid oily matter, sooner than in a furnace oil can be extracted out of a plant. _A._ But if the water be above the fire in a kettle, what then will it do? Shall the particles of water go toward the fire, as it did toward the sun? _B._ No. For it cannot. But the motion of the parts of the kettle which are caused by the fire, shall dissipate the water into vapour till it be all cast out. _A._ What is that you call fire? Is it a hard or fluid body? _B._ It is not any other body but that of the shining coal; which coal, though extinguished with water, is still the same body. So also in a very hot furnace, the hollow spaces between the shining coals, though they burn that you put into them, are no other body than air moved. _A._ Is it not flame? _B._ No. For flame is nothing but a multitude of sparks, and sparks are but the atoms of the fuel dissipated by the incredible swift motion of the movent, which makes every spark to seem a hundred times greater than it is, as appears by this; that, when a man swings in the air a small stick fired at one end, though the motion cannot be very swift, yet the fire will appear to the eye to be a long, straight, or crooked line. Therefore a great many sparks together flying upward, must needs appear unto the sight as one continued flame. Nor are the sparks stricken out of a flint any thing else but small particles of the stone, which by their swift motion are made to shine. But that fire is not a substance of itself, is evident enough by this, that the sun-beams passing through a globe of water will burn as other fire does. Which beams, if they were indeed fire, would be quenched in the passage. _A._ This is so evident, that I wonder so wise men as Aristotle and his followers, for so long a time could hold it for an element, and one of the primary parts of the universe. But the natural heat of a man or other living creature, whence proceedeth it? Is there anything within their bodies that hath this compounded motion?