It was not till man began to bore into the Earth for metallic or potable purposes that he brought to light the generic fact that it was everywhere hotter as one went down. And this not only in a very regular, but in a most speedy, manner. The temperature increased in a really surprising way 1° F. for every sixty-five feet of descent. As the rise continued unabated to the limit of his borings, becoming very unpleasant at its end, it was clear that at a depth of thirty-five miles even so refractory a substance as platinum must melt, and practically all the Earth except a thin crust be molten or even gaseous. Now heat, like money, is easy to dissipate but hard to acquire, as primitive man was the first to realize. It does not come without cause. Being a mode of motion, other motion must have preceded it from which it sprang. So much the doctrine of the conservation of energy teaches us, a doctrine considered now to have been the great scientific heirloom of the nineteenth century to the twentieth, yet which in its day caused the death of its first discoverer, Mayer, of a broken heart from non-recognition; its second, Helmholtz, was refused publication by the leading Berlin physical magazine of the time. So quick is man to delay his own advance. The only conceivable motion for thus heating the Earth as a whole was the falling together of its parts. The present heat of the Earth, then, accuses the concourse of particles in the past to its formation, or in other words proves that the Earth was evolved out of material originally more sparcely strewn. It does so not only in a generic but in a most particular manner, for the heat is distributed just where it would be by such a process. It is greater to-day within, increasingly, because when the globe began to cool, the surface necessarily cooled first and established a regular gradient of heat from core to cuticle.