TRIPOLY TO BENGAZI. 129 wards took the precaution of dismounting when we had occasion to cross any part which was considered to be dangerous. We found on examination that many hollow spaces of considerable depth and extent existed in various parts of the marsh ; and that the crust of salt and mud which covered them was sometimes no more than two inches, and an inch and a half, in thickness.

These usually occurred in the most level parts, but as the crust was everywhere in appearance the same, there were no means of ascertaining where they existed, but by breaking the surface which concealed them.

The water contained in these hollows was invariably salt, or very brackish ; it was usually clear, and was in some places deep : the depth of mud below the water must also have been sometimes considerable, and the vacant space contained between the outer surface of the marsh and the water was in various instances observed to be as much as twelve and fifteen feet in depth. We had no means of ascertaining the depth of the water in the hollow alluded to above ; but the space between its surface and that of the marsh appeared to be more than twelve feet, and, from the sound occasioned by the fall of the pieces into it, its depth could scarcely have been less than six or eight feet. In that part of the marsh which surrounds the Gusser el Jebha the nature of these pits is very apparent ; for the ground being unequal, and overgrown with reeds and brushwood, no crust has been formed over them, and their dimensions are therefore easily ascertained. They are here very numerous, and it would be scarcely possible to escape falling into them after dark, as s