96 Sir Charles A. Parmns [March 10, 



In models, and in vessels of moderate speed, the forces are not 

 snflficient to tear the water asunder, hat if the pressure of the atmo- 

 sphere is removed, a model screw will cavitate at a comparatively 

 moderate speed. 



The marine turl)ine, with the modifications we have so far described, 

 is only suitable for vessels of more than 16 knots sea speed, and to 

 make it suitable for the remainini; two-thirds of the tonnage of the 

 world has been our constant aim. The first plan to this end to be 

 adopted is somewhat in the nature of a compromise, and is called the 

 combination system, because the reciprocating engine is used to take 

 the first part of the expansion and the turbine to complete it. From 

 what we have said it will be apparent that this coalition of the 

 reciprocating engine and turbine is a good one, because they each work 

 under advantageous conditions. The reciprocating engine expands 

 the steam to about atmospheric pressure, and the turlnne carries on 

 the expansion with high efficiency down to the pressure in the 

 condenser. Now, though a large and high-speed turbine deals with 

 the high-pressure portion of the expansion 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 better than any reciprocating engine. In 

 this system the turbine develops about one-third of the whole power. 



Aljout fifteen years ago I filed a patent for the system, but, with 

 the exception of fitting the British iVdmiralty destroyer Velox in 1902, 

 few steps were taken towards its application until the turbine had 

 become firmly established for fast vessels, because we feared the 

 technical public would say, " You are trying to bolster up a failure of 

 the turbine." About three years ago Messrs. Denny, of Dumbarton, 

 who in 1901 built the first mercantile turbine vessel, the King Edward, 

 built the first combination vessel, the Otaki, of 9900 tons dead- 

 weight capacity and 13 knots sea speed. She has ordinary twin screws 

 driven by triple-expansion engines exhausting into a turbnie driving a 

 central screw. The initial pressure at the turbine is 9 lbs. al)Solute, 

 and it generates one-third of the whole power. The coml)ination 

 vessel was found to consume 12 per cent, less coal on service than her 

 sister vessel Orari on the same service, fitted with quadruple recipro- 

 cating engines. 



Th(! next combination vessel was the Laurentk, of 20,000 tons, 

 l)uilt by Messrs. Harland and Wolft", a sister vessel, the Metjanik, 

 being fitted with quadruple engines, and on service at the same speed 

 the saving in coal by the combination is 11 per cent. 



Messrs. Harland and Wolff are also fitting the coml)ination system 

 in the White Star liners Oli/mpir and IHtttnic of 60,000 tons displace- 

 ment, and some otiier companies at home and aliroad are also adopting 

 the combination system. 



There is another alternative solution which promises to extend the 

 field of the turbine further uvei- that of the reciprocating engine. 



