242 Hon. C. A. Parsons [Jan. 26, 



centrifugal pumps for lifts up to 200 feet, and screw pumps for 

 low lifts. 



The most important field, however, for the steam turbine is 

 undoubtedly in the propulsion of ships. The large and increasing 

 amount of horse-power and the greater size and speed of the modern 

 engines tend towards some form which shall be light, capable of 

 perfect balancing aud economical in steam. The marine engine of 

 the piston type does not entirely fulfil all these requirements, but the 

 compound turbine engine, as made in 1892, appeared to be capable 

 of doing so, and of becoming an ideal marine engine. On the other 

 hand, an element of uncertainty lay in the high speed of the turbine 

 engine, and to couple it directly to a propeller of ordinary propor- 

 tions would have led to failure. 



In January 1894, a pioneer syndicate was formed to explore the 

 problem, those chiefly associated in the undertaking being the Earl 

 of Rosse, Christopher Leyland, John Simpson, Campbell Swinton, 

 Norman Cookson, the late George Clayton, H. C. Harvey, and Gerald 

 Stoney. It was deemed expedient, for reasons of economy and also 

 of time (as many alterations were anticipated), to build as small a 

 vessel as possible, but not so small as to preclude the attainment 

 of an unprecedented high speed in the event of success. The Turbinia 

 was constructed, her dimensions being 100 feet in length, 9 feet 

 beam, 3 feet draught of hull, and 44 tons displacement. She was 

 fitted with a turbine engine of 2000 actual horse-power, with an 

 expansive ratio of a hundred-and-fifty-fold, also with a water-tube 

 boiler of great power, of the express type, with small tubes. The 

 turbine engine was designed to drive one screw shaft at a speed 

 of from 2000 to 3000 revolutions per minute. 



Many trials were made with screw propellers of various sizes and 

 proportions, but the best speeds were quite disappointing, and it was 

 clear that some radical defect lay in the propellers. This was corrobo- 

 rated by dynamoinetric measurements'. The excessive slip of the pro- 

 pellers beyond the calculated amount, and their inefficiency, indicated 

 a want of sufficient blade area upon which the thrust necessary to 

 drive the ship was distributed — in other words, the water was torn into 

 cavities behind the blades. These cavities contained no air, but 

 only vapour of water, and the greater portion of the power of the 

 engine was consumed in the formation and maintenance of these 

 cavities instead of the propulsion of the vessel. This phenomenon was 

 first noticed in the trials of the torpedo-boat Daring, by Messrs. 

 Thornycroft and Mr. Barnaby, shortly before the commencement of 

 the trials of the Turbinia, and was named " cavitation " by Mr. R. E. 

 Froude. 



This phenomenon has been investigated experimentally with pro- 

 pellers of small size working inside an oval tank, so as to represent 

 approximately the conditions of slip ratio customary in fast ships. To 

 enable the propeller to cause cavitation more easily the tank is closed 

 and the atmospheric pressure removed from the surface of the water 



