STEAM TURBINES AND HIGH-SPEED VESSELS. 703 



water at and just below the boiling point, dynamometric measure- 

 ments being taken of power and thrust with various widths of pro- 

 peller blade, the conclusion arrived at being that wide and thin 

 blades are essential for fast speeds at sea, as well as a coarse pitch 

 ratio of propeller. 



The first vessel fitted with steam turbine machinery was the 

 Turbinia. She was commenced in 1894, and, after many altera- 

 tions and preliminary trials, was satisfactorily completed in the 

 spring of 1897. Her principal features are: Length, one hundred 

 feet; beam, nine feet; five-foot draught of water under the pro- 

 pellers; forty-four tons and a half displacement on trial; she is 

 fitted with a water-tube boiler of eleven hundred feet total heating 

 surface, and forty-two square feet of grate area, with closed stoke- 

 holds supplied with air from a centrifugal fan mounted on a pro- 

 longation of the low-pressure turbine shaft. The engines consist 

 of three compound steam tui*bines, high pressure, intermediate, 

 and low pressure, each driving one screw shaft; on each of the 

 shafts are three propellers, making nine in all; the condenser is 

 of the usual type, and has four thousand square feet of surface. 



When officially tested by Professor Ewing, F. R. S., assisted by 

 Professor Dunkerley, she attained a mean speed on a measured 

 mile of thirty-two knots and three quarters, and the consumption 

 of steam for all purposes was computed to be fourteen pounds and 

 a half per indicated horse power of the main engines. Subse- 

 quently, after some small alterations to the steam pipe, she was 

 further pressed, and is estimated to have reached ihe speed of 

 thirty-four knots and a half. She was, and still is, therefore, the 

 fastest vessel afloat; she has been out in very rough weather, is 

 an excellent sea boat, and at all speeds there is an almost complete 

 absence of vibration. 



In the Turbinia the exceptional speed results principally from 

 two causes: 1. The engines, screws, and shafting are exceptionally 

 light. 2. The economy of steam in the main engines is greater 

 than usual. 



At full speed the steam pressure in the boiler is two hundred 

 and ten pounds; at the engines, one hundred and seventy-five; and 

 the vacuum in the condenser twenty-seven inches, representing an 

 expansion ratio in the turbines of about one hundred and ten after 

 allowance has been made for wire-drawing in the exhaust pipe. 



The first vessels of larger size than the Turbinia to be fitted 

 with steam turbine machinery are the torpedo-boat destroyer "Viper 

 for the British Government, and a similar vessel for Messrs. Sir 

 W. G. Armstrong, Whitworth & Company. 



These vessels are of approximately the same dimensions as the 



