OF THE MINERAL WORK.

the center, how is it that the whole thing does not become hot from it, or at least as much as it is hot around the surface, since experience testifies that the excavated earth is not hot, but cold, and no heating rays are found in it? Take this answer: scattered rays of the sun exercise their powers only in those places where they are collected and become sensible. The traces of this can be observed on the surface itself, which does not permit them such a fast passage, but because of its hardness and the density of stones, it halts and delays them for some time. Whence the heat is doubled and multiplied, so that to the very hard rocks and crags such fervor sometimes arises from the incessant and crowded influx and condensation of rays that wood or straw brought near by chance might ignite and burn, which never happens in the rare and porous air—which is incapable of halting those rays—even if it is closer to the sun. For the higher you ascend into the Air, the more intensely you will feel the cold, so that the highest mountains, even if situated in hot regions, are always rigid with snow, ice, and frost, while only the roots are intensely hot and produce various fruits, even though they are further from the sun. The sole cause of this cold at the peak and heat at the root is the reflection of the solar rays, which settle there and are multiplied, which cannot happen in any way in the highest air. When these rays have first penetrated the surface of the earth, they are only joined and multiplied at the surface, and they gradually weaken, returning to simplicity. Whence it is that the part of the earthly globe located further from the center hardly