I found some rain water, in clay pans, upon it.

A clay pan is a small area of ground, whose top soil has been washed or blown away, leaving the hard clay exposed; and upon this surface, one, two, three, or (scarcely) more inches of rain water may remain for some days after rain: the longer it remains the thicker it gets, until at last it dries in cakes which shine like tiles; these at length crumble away, and the clay pan is swept by winds clean and ready for the next shower.

In the course of time it becomes enlarged and deepened.

They are very seldom deep enough for ducks.
The grass and herbage here were excellent.

There were numerous kangaroos and emus on the plain, but they preferred to leave us in undisturbed possession of it.