We breakfasted by candle-light and then set off into the chilly dawn. Harvey had urged on us the wisdom of starting early, for the way to Tozeur lies across the salt lakes of the Djerid, a dismal and treacherous morass which is none too safe by day and exceedingly perilous after nightfall. These salt lakes form one of the most singular features of the Tunisian Sahara, stretching in a charm which has only two short breaks right across the southern end of the regency from the Gulf of Gabés to the frontier of Algeria, which they penetrate for a considerable distance. They are called by the French (with their usual inaccuracy of spelling and pronunciation) _chotts_, whereas the word should really be the Arabic _shat_, the native term for a broad canal, a lake, an estuary. Strictly speaking, however, the shats are not lakes at all at the present day, but shallow depressions, some feet below sea-level, which during more than half the year are expanses of dried mud thickly incrusted with white salt, this saline veneer giving them at a little distance the appearance of broad sheets of ice or water. During the winter, however, when the effect of the rare rains is felt, the shats frequently contain several feet of water, which, by liquefying the mud into a quicksand, makes them quite impassable for man or beast. But during the other seven months of the year they can be crossed on foot or horseback, and, when the sun has baked the surface to a sufficient hardness, a motor-car may venture on them with reasonable safety. Even during the dry months, however, the shats are exceedingly treacherous; surfaces which give every indication of solidity at a few yards’ distance are often but thin crusts which will give way without the slightest warning beneath the weight of animals or men, precipitating them into a sea of slime from which escape is frequently impossible. One hears innumerable stories of the tragedies which have been enacted in the shats. “A caravan of ours,” relates one Arab writer, “had to cross the shat one day; it was composed of a thousand baggage-camels. Unfortunately one of the beasts strayed from the path, and all the others followed it. Nothing in the world could be swifter than the manner in which the crust yielded and engulfed them; then it became like what it was before, as if the thousand camels had never existed.”