Great quantities of it were found on the floors of caves which had not been occupied by man.

It is not of a sandy nature, and its colour is light brown, sometimes almost grey, or even white.

The ancient builders simply had to mix it with water and mould it into bricks, which, though fairly uniform in thickness, were very irregular in size.

There were no marks of implements on the walls; all the work seems to have been done by hand and smoothed over with some wetted fabric.

In one cave of this valley the walls show finger-marks on the plaster.