Page:The Steam Turbine.djvu/59

 as economically as a reciprocating engine, a slow speed turbine cannot be made to do so, but on the other hand a slow speed turbine expands low pressure steam much further and more economically than any reciprocating engine. Under this system the turbine generally is made to develop about one-third of the whole power.

About 15 years ago this plan was worked out and the British Admiralty destroyer "Velox" was so fitted in 1902 (page 43), but no further practical steps were taken towards its application until about three years ago.

Messrs Denny of Dumbarton, who in 1901 built the first mercantile turbine vessel, the "King Edward," in 1908 built the first combination vessel, the "Otaki" of 9,900 tons and 13 knots speed. She has ordinary twin screws driven by triple expansion engines which exhaust into a turbine driving a central screw as illustrated on the next page. The initial pressure at the turbine is 9 lbs. absolute, and it develops one-third of the whole power. This combination vessel was