Page:Popular Science Monthly Volume 64.djvu/189

Rh. In fact, the list of boiler explosions, with their attendant loss of life and property, is a list of failures of the shell-boiler. Admiral Melville brought this 'new' boiler into permanent employment a hundred years after Stevens and made its value and necessity evident. The battle-ship or cruiser of to-day could not be constructed of equal speed, and equal efficiency of armor and armament, without it, and all navies are now adopting it. It gives a minimized weight and space for the unit of power, is safe against the disastrous explosions characterizing so frequently the termination of the work of the shell-boiler, and it is economical. It may be employed for pressures of any degree of intensity. The battle-ship of to-day could not attain its actual effectiveness without its employment, at least as a battery for high speeds. At cruising speeds, the older boiler is often retained; the later type being brought into operation when driving the ship up to emergency speed. The water-tube boiler requires more skill in handling than the fire-tube.

Melville introduced the triple-screw system for large ships, in which it was becoming difficult to secure safe construction of the enormous propeller-shafts demanded, and where it seemed to him desirable to secure a better hold upon the water by enlarging the area of the current utilized in propulsion. The success of the Columbia and the Minneapolis, fast cruisers, was complete, breaking the record for naval craft of large size and exceeding by a knot the speed anticipated even by their designer. He introduced the 'repair-ship,' a floating machine-shop, and the 'distilling ship,' in the war with Spain, as adjuncts to the fleet, innovations, both, of great value, often of vital importance.

In the details of his work, the chief of bureau has always exhibited the most thorough familiarity with its scientific side, and his plans have always involved the employment of every expedient known to science for promotion of efficiency. He has advocated increased thermodynamic range, higher ratios of expansion and greater piston-speeds for his engines, to give increased thermodynamic efficiency; has made effective provision against those extra-thermodynamic wastes which constitute the most serious tax upon heat utilization and has adopted every sound system of improvement known to modern science as bearing upon his work.

One of his most important movements was that in promotion of the merging of the old engineer corps of the navy into the line. The battle-ship has long been recognized as what the writer has called the