The supplying of the troops at Suakim and in the Soudan with water is one of the most important items in the whole conduct of the Egyptian war. Even in cold or temperate latitudes fresh water is a first necessity for animal life; much more is this the case in the desert; and the wells in the country forming the scene of our military operations form in themselves valuable strategical points. Their supply, however, has to be supplemented, and to do so artificial means and the aid of the engineer have to be enlisted into this service. Many of our readers see notices from time to time in the newspapers about this or that ship being employed, or at least her steam fittings, in distilling water for the use of the troops; and although most of, if not all, our readers are engineers, still it is no disparagement to some of them to assume that they are more or less unfamiliar with sea water distillation on the scale on which the process is now being carried on at Suakim; and as the subject is of general interest, we give a short description of the process. In a general sense, fresh water is obtained from sea water by simply generating steam from the sea water, passing the said steam through a surface condenser, and filtering the resulting water. The obtaining of fresh water in this way has been in practice on board sea-going ships for many years. It is supposed by some authorities on this subject that the first time fresh water was thus obtained at sea was by an old captain of a brig which ran short of water, and he cut up some pewter dishes into strips, which he bent and soldered into a pipe. He, with the carpenter's aid, fitted a wooden lid in one of the cooking boilers, and fixed one end of his pipe in it. He next sawed a water cask in half, bored a hole in the bottom of one half, and took his pipe through it, filling the space round the pipe with sea water. Thus he extemporized a worm and still or condenser. The distilled water, however, was scarcely drinkable. Not to be beaten, however, the captain got some pieces of charred wood which he put in the water, which so far improved it as to render it at all events fit to sustain life, and our skipper brought his brig and her screw safely to port. What suggested the use of charcoal to his mind history does not tell. For many years past scarce any sea-going vessel leaves port that is not fitted with a properly constructed distiller; and one conspicuous advantage attending this practice is that each ship thus fitted to the satisfaction of the Board of Trade inspector is allowed to sail with only half the quantity of fresh water on board which she should have if not provided with a distiller. The distiller and filter occupy very much less space than that which would be occupied by the casks or tanks of water otherwise required to be carried.