When they saw the clear sandy bottom of the central burn they readily went in, but usually plunged right over head, leaving their tail up in the air to show the nervous shock they had sustained.
These sponges are a serious matter in travelling.

I crossed the twenty-nine already mentioned at the end of the fourth month of the dry season, and the central burns seemed then to have suffered no diminution: they were then from calf to waist deep, and required from fifteen to forty minutes in crossing; they had many deep holes in the paths, and when one plumps therein every muscle in the frame receives a painful jerk.

When past the stream, and apparently on partially dry ground, one may jog in a foot or more, and receive a squirt of black mud up the thighs: it is only when you reach the trees and are off the sour land that you feel secure from mud and leeches.

As one has to strip the lower part of the person in order to ford them, I found that often four were as many as we could cross in a day.

Looking up these sponges a bird's-eye view would closely resemble the lichen-like vegetation of frost on window panes; or that vegetation in Canada-balsam which mad philosophical instrument makers _will_ put between the lenses of the object-glasses of our telescopes.