6 ft. 2 in. high, and weighing about 23 cwt., will give 85 gallons; while a still larger one, measuring 7 ft. high and weighing 32 cwt., yields 150 gallons.  These have no pumps.  When an engine and pump are fitted, the weight is increased from about 80 per cent. in the smaller to 50 per cent. in the larger sizes.  An immense advantage attends the use of those distillers that are combined with a winch boiler.  Of course, the chief use of the winch is while in dock; some use is made of it at sea to do heavy pulling and hauling, to wash decks, and in case of emergency the circulating pump is used as a fire engine.  Were it not, however, for the distiller, the winch boiler would simply be idle lumber at sea.  The distiller, however, finds useful employment for it, and has also this excellent effect, that as steam is pretty constantly kept up for the distiller, in the evil event of a fire the boiler is ready to work at once.  In horizontal types of distiller an engine and pump are mounted on a cast iron casing as a bed, and in this casing is placed a number of tubes through which the steam passes to be condensed, the whole being simply a surface condenser with engine and pump above.  Another type is that of a small single-flued horizontal boiler with combustion chamber and twenty or thirty return tubes—­in fact, the present high-pressure marine boiler on a small scale.  A boiler of this sort, measuring 4 ft. to 5 ft. long, 3 ft. 9 in. to 4 ft. 6 in. diameter, would have a horizontal donkey engine on a bed at its side, and at the end of the engine a vertical cylindrical condenser.

[Illustration]

Few have done more, perhaps none so much, as Dr. Normandy to make sea water distillation not only a success as a source of water supply, but also to supply it at a minimum cost for fuel.  He by a peculiar arrangement of pipes embodied something of the regenerative system in his apparatus, using the heat taken from one lot of steam to generate more, and again the heat from this he used over again.  The defect of his older arrangements was undue complexity and consequent trouble to keep in order.

As can be well imagined, the distillers in use at Suakim are on a much more colossal scale, and owing to the now almost universal use of surface condensers in ocean steamers, no great difficulty ought to attend the adaptation of the boilers and condensers of one of our transports.  One of these full-powered steamers will indicate, say, 5,000 horse-power, and assuming her engines to use 25 lb. of steam per indicated horse-power, or 21/4 gallons, she could distill some 12,000 gallons of water per hour.  As no appreciable pressure of steam need be maintained, the boilers would suffer little from deposit, especially if regularly blown out.  Hard firing need not be resorted to; indeed, it would be injudicious, as, of course, priming must be carefully guarded against.  Of course, the salt water distilled will affect the working, not exactly of the distillers, but of the boilers.