Page:The Development of Navies During the Last Half-Century.djvu/281

 beam, and 32 tons displacement, attained a mean speed of over 18 knots. Her engines, supplied by her builders, were compound, driving a single screw. The high-pressure cylinder was 12¾ in. in diameter, the low-pressure 21 in., their stroke was 12 in. She had a steel boiler of the modified locomotive pattern, working at 120 lbs. pressure. Her surface condenser was made of thin sheet copper, and was supplied with a separate engine and centrifugal pump. The machinery of this vessel was very light, steel being largely used, and the workmanship was of the highest class. She was, in her day, a complete novelty, both as regards hull and machinery, and was equally a complete success. She is interesting as the pioneer of a very numerous and important flotilla. By May 1887 Messrs Yarrow, of Poplar, who have always been friendly rivals of Messrs Thorneycroft, had supplied our navy with a torpedo boat, known as 'No. 80,' which illustrates the strides that had been made by both firms in a decade. This vessel has a length of 135 ft., beam of 14 ft., and displacement of about 130 tons. Her triple-expansion engines work up to 1700 indicated horse power, and the trial speed for three hours was 23 knots. She can steam a distance of 2000 knots at 11 knots speed. There is only one locomotive boiler, and it is probable the boilers of this type of boat are the largest ever built on the locomotive principle, but the firm has as yet had no failures with them. Higher speeds with more powerful machinery have been attained in boats built since 'No. 80' by both firms for foreign powers. Messrs Yarrow have recently