_B._ Then that is it you would know the cause of. I have told you before that by the motion I suppose both in the sun, and in the earth, the air is dissipated, and consequently that there would be an infinite number of small empty places, but that the world being full, there comes from the next parts other air into the spaces they would else make empty. When therefore this motion of the sun is exercised upon the superficies of the earth, if there do not come out of the earth itself some corporal substance to supply that tearing of the air, we must return again to the admission of vacuum. If there do, then you see how by this motion fluid bodies are made to exhale out of the earth. The like happens to a man’s body or hand, which when he perceives, he says he is hot. And so of the earth when it sendeth forth water and earth together in plants, we say it does it by heat from the sun. _A._ It is very probable, and no less probable, that the same action of the sun is that which from the sea and moist places of the earth, but especially from the sea, fetcheth up the water into the clouds. But there be many ways of heating besides the action of the sun or of fire. Two pieces of wood will take fire if in turning they be pressed together. _B._ Here again you have a manifest laceration of the air by the reciprocal and contrary motions of the two pieces of wood, which necessarily causeth a coming forth of whatsoever is aereal or fluid within them, and (the motion pursued) a dissipation also of the other more solid parts into ashes. _A._ How comes it to pass that a man is warmed even to sweating, almost with every extraordinary labour of his body? _B._ It is easy to understand, how by that labour all that is liquid in his body is tossed up and down, and thereby part of it also cast forth. _A._ There be some things that make a man hot without sweat or other evaporation, as caustics, nettles, and other things. _B._ No doubt. But they touch the part they so heat, and cannot work that effect at any distance. _A._ How does heat cause light, and that partially, in some bodies more, in some less, though the heat be equal? _B._ Heat does not cause light at all. But in many bodies, the same cause, that is to say, the same motion, causeth both together; so that they are not to one another as cause and effect, but are concomitant effects sometimes of one and the same motion. _A._ How?