The Desert journey from Korosko is not an affair to be undertaken carelessly and without thoughtful preparation. The distance is about two hundred and fifty miles, and is traversed in eight days. It is necessary to carry water in goat-skins all the way, as there is only one well or spring on the route, and the water from it is undrinkable by man, and only endurable by the powerful stomach of the camel. Of course, the supply was used very sparingly; washing, except in sand, was quite out of the question, and as none of the party had a fondness for the sand-bath, they made no ablutions till reaching the Nile once more, except to moisten their eyes in the morning. The skins of water were distributed upon the camels, and each of the travellers had a small skin hanging at his saddle-bow for a daily supply. By the advice and example of the Doctor each of the boys had an extra skin of water hidden in his baggage, and its existence was carefully concealed from the Arab drivers. These fellows are inclined to improvidence, and had they known of this private provision they would have been certain to count it as part of the regular supply, and expect to draw upon it. The heat of the Desert and the glare of the sun incline the traveller to thirst, and perhaps the knowledge of the necessity for economy is an additional incentive to it. Human nature has curious ways, and the desire for a thing generally increases in proportion to the difficulty of procuring it. Frank and Fred found that the fact of the scarcity of water, and the necessity of limiting their use of the precious fluid, increased their longing for it. At first they yielded by taking occasional draughts, but very soon they decided upon the old expedient of chewing a bit of leather or some other hard substance, to create a flow of saliva to moisten their lips. With a little self-denial, aided by the above practice, they soon conquered their thirst, and were able to get along nearly as well as the Arabs who accompanied them. Frank intimated that the warmth of the water, and the flavor of goat-skin which it soon acquired, had a material influence in lessening his desire for it. The dreary waste of sand was partially relieved here and there by ranges of hills or low mountains, but they were barren as the rest of the Desert, and therefore made comparatively little variation in the landscape. There was not a cloud in the sky, and the sun poured its blistering rays upon the travellers during all the time it was above the horizon. In the morning and evening the heat was not intense, but in the middle of the day it was like the blast of a furnace.