A third, seen more rarely, is as large as a pigeon, and is of a slaty color.
Another inhabitant of the banks is the sand-martin, which also likes company in the work of raising a family.

They never leave this part of the country.

One may see them preening themselves in the very depth of winter, while the swallows, of which we shall yet speak, take winter trips.

I saw sand-martins at the Orange River during a period of winter frost; it is, therefore, probable that they do not migrate even from thence.
Around the reeds, which in some parts line the banks, we see fresh-water sponges.

They usually encircle the stalk, and are hard and brittle, presenting numbers of small round grains near their circumference.
The river was running at the rate of five miles an hour, and carried bunches of reed and decaying vegetable matter on its surface; yet the water was not discolored.