Hermann von Helmholtz

The older view of the nature of heat was that it is a substance, very fine and imponderable indeed, but indestructible, and unchangeable in quantity, which is an essential fundamental property of all matter.

Heat can also be produced by the impact of imperfectly elastic bodies as well as by friction. This is the case, for instance, when we produce fire by striking flint against steel, or when an iron bar is worked for some time by powerful blows of the hammer.

One of the best known, and one of the least intelligible, facts of literary history is the lateness, in Western European Literature at any rate, of prose fiction, and the comparative absence, in the two great classical languages, of what we call by that name.