1. Why breath from the same mouth sometimes heats and sometimes cools.—2. Wind, and the inconstancy of winds, whence.—3 Why there is a constant, though not a great wind, from east to west, near the equator.—4. What is the effect of air pent in between the clouds.—5. No change from soft to hard, but by motion.—6. What is the cause of cold near the poles.—7.. The cause of ice; and why the cold is more remiss in rainy than in clear weather. Why water doth not freeze in deep wells as it doth near the superficies of the earth. Why ice is not so heavy as water; and why wine is not so easily frozen as water.—8. Another cause of hardness from the fuller contact of atoms; also, how hard things are broken.—9. A third cause of hardness from heat.—10. A fourth cause of hardness from the motion of atoms enclosed in a narrow space.—11. How hard things are softened.—12. Whence proceed the spontaneous restitution of things bent.—13. Diaphanous and opacous, what they are, and whence.—14. The cause of lightning and thunder.—15. Whence it proceeds that clouds can fall again after they are once elevated and frozen.—16. How it could be that the moon was eclipsed, when she was not diametrically opposite to the sun.—17. By what means many suns may appear at once.—18. Of the heads of rivers. [Sidenote: Why breath from the same mouth sometimes heats and sometimes cools.] 1. As, when the motion of the ambient ethereal substance makes the spirits and fluid parts of our bodies tend outwards, we acknowledge heat; so, by the endeavour inwards of the same spirits and humours, we feel cold. So that to cool is to make the exterior parts of the body endeavour inwards, by a motion contrary to that of calefaction, by which the internal parts are called outwards. He, therefore, that would know the cause of cold, must find by what motion or motions the exterior parts of any body endeavour to retire inwards. To begin with those phenomena which are the most familiar. There is almost no man but knows, that breath blown strongly, and which comes from the mouth with violence, that is to say, the passage being strait, will cool the hand; and that the same breath blown gently, that is to say, through a greater aperture, will warm the same. The cause of which phenomenon may be this, the breath going out hath two motions; the one, of the whole and direct, by which the foremost parts of the hand are driven inwards; the other, simple motion of the small particles of the same breath, which, (as I have shown in the 3rd article of the last chapter, causeth heat. According, therefore, as either of these motions is predominant, so there is the sense sometimes of cold, sometimes of heat. Wherefore, when the breath is softly breathed out at a large passage, that simple motion which causeth heat prevaileth, and consequently heat is felt; and when,