revolve about the sun, traversing with very variable velocities
extremely elongated orbits."[2]

We shall see reason to believe that they contain the same kinds of
substances of which the planets are composed.

Their orbits seem to be reminiscences of former planetary conditions:

"All the comets, having a period not exceeding seven years, travel in
the same direction around the sun as the planets. Among comets with
periods less than eighty years long, five sixths travel in the same
direction as the planets."[3]

[1. "American Cyclopædia," vol. v, p. 141.

2. "The Heavens," p. 239.

3. American Cyclopedia," vol. v, p. 141.]

{p. 71}

It is agreed that this globe of ours was at first a gaseous mass; as
it cooled it condensed like cooling steam into a liquid mass; it
became in time a molten globe of red-hot matter. As it cooled still
further, a crust or shell formed around it, like the shell formed on
an egg, and on this crust we dwell.

While the crust is still plastic it shrinks as the mass within grows
smaller by further cooling, and the wrinkles so formed in the crust
are the depths of the ocean and the elevations of the mountain-chains.