"Why, a flash of lightning, of course!"
"Naturally! but what is the nature of that flash?"
"Why, I always supposed that all flashes were alike."
"That shows how much you know!" answered Cornelius, in a tone of disgust. "Now, there are several classes of lightning; for instance, lightning of the first class is generally in the form of a luminous furrow and is very crooked and forked, affecting a zig-zag movement, and of a white or purple color; then, there is the lightning of the second class, an extended sheet of flame, usually red, and which embraces the entire horizon in circumference; and finally, lightning of the third class, which is invariably in the form of a rebounding, rolling, spherical body; the question is whether it is really globular in shape or merely an optical illusion? This is exactly the problem I have been trying to solve! I suppose you will say that these globes of fire have been sufficiently observed by Howard, Schübler, Kamtz—"
"Oh, I don't know anything at all about such rot, so I won't venture an opinion. The rain is coming down again and I want to go home."
"Wait a moment," calmly replied Cornelius; "and as soon as I have seen a spherical or globular flash I will—"
"I have n't time to wait: besides, I would be
