VARIETIES OF LIGHTNING.
According to Arago’s investigations, the evolution of Lightning is of three kinds: zigzag, and sharply defined at the edges; in sheets of light, illuminating a whole cloud, which seems to open and reveal the light within it; and in the form of fire-balls. The duration of the first two kinds scarcely continues the thousandth part of a second; but the globular lightning moves much more slowly, remaining visible for several seconds.