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 boilers but also for the use of the crew. The newest of these, and apparently by a long way the most efficient, is the Yaryan, of American origin, the main principle of which is that the sea water before being evaporated and condensed is pulverised into spray. Professor Lewes, of the Royal Naval College, speaking of most of the other varieties, averred with good reason that the trouble of deposit in the boilers was only transferred to the distillery apparatus; in the Yaryan there has been no trouble at all, because there has been no deposit.

Looking back, then, on the past half century, we find that the whole aspect of marine engineering has changed. And nowhere is this revolution more distinctly marked than in the Royal Navy, where it has produced its most startling effects. In the early days the steam engine was seldom used, and occupied a very minor position in the internal arrangement of a ship, but now it is absolutely requisite for every purpose for which the modern man-of-war exists. Steam machinery now fulfils every function of the latter-day ironclad. Its very air and light, its steering and anchoring, the training and loading of its guns, the motive power of its torpedoes, all these, and many other things, without steam could not be. As a matter of course, as steam machinery became of more and more importance in the navy, so did the position of the officers in charge of it advance. Before 1847 all engineers were warrant officers, but junior of that rank, so that the chief engineer of a paddle-wheel frigate was then, officially, of less account than the carpenter. He is now, as far