es. A million columns rise, so thick at the
top that they make twilight at mid-day, and their trunks are so close
together we can scarcely edge our way between them, whilst the ground is
carpeted with trailing plants completely interwoven. What strange trees
they are! Beneath us lies an accumulation of vegetable matter more than
200 feet in thickness--the result of the growth and decay of plants in
this swamp for centuries. All things are here favourable for the growth
of vegetation--the great heat of the ground causes water to rise rapidly
in vapour, and this again descends in showers, supplying the plants with
moisture continuously. The air contains a large proportion of carbonic
acid gas, poison to animals but food to plants, which, by means of its
aid, build up their woody structure. Winds at times level these gigantic
plants, for their hold on the earth is feeble, and thus the mass goes on
increasing.

We are now on the edge of a lake abounding with fish, whose bony scales
glitter in the water as they pursue their prey. Lying along the shore
are shells cast up by the waves, and there are also seen the tracks of
some large animals. How like the impression of a man's hand some of
these tracks are! The hind-feet are evidently much larger than the
fore-feet. There is the frog-like animal which made them, and what a
size! It must be six feet long, and its head looks like that of a
crocodile, for its jaws are furnished with formidable rows of long,
strong, sharp, conical teeth.

The continued growth and decomposition of the vegetation during long
ages must have produced beds like the peat-deposits of America and Great
Britain. In the Dismal Swamp of Virginia there is said to be a mass of
vegetable matter 40 feet in thickness, and on the banks of the Shannon
in Ireland is a peat-bog 3 miles broad and 50 feet deep. When conditions
were so much more favourable for these deposits, beds 400 feet in
thickness may easily have been produced. This accumulated mass of
vegetable matter must be buried, however, before we can have a coal-bed.
How was this accomplished? The very weight of it may have caused the
crust of the earth to sink, forming a basin into which rivers, sweeping
down from the surrounding higher country, and carrying down mud in their
waters, the weight of which, deposited upon the vegetable matter,
pressed and squeezed it into half its original compass. Sand carried
down subsequently in a similar manner, and depos