530 The Hon. Charles A. Parsons [May 4, 



ciprocating engine, from its nature, can only take full advantage of 

 about two-thirds of the whole range of expansion, and is unable 

 to deal usefully with very low vapour densities — the low-pressure 

 cylinders cannot (because of structural difficulties) be made large 

 enough, and the last part of the expansion has to be allowed to run 

 to waste. 



The growth in size of the turbine is perhaps interesting. The 

 first practical steam turbine, constructed in 1884, was of 10 horse- 

 power. By 1892 the largest size for driving dynamos had reached 

 200 horse-power. It has been continuously increasing, and has now 

 reached 12,000 horse-power in one unit driving one alternating 

 dynamo. 



In 1894 the " Turbinia," of 2000 I.H.P. was commenced. The 

 diagram, Fig. 5, shows her low-pressure and reversing turbine. 

 The L.P. turbine is 3 feet in diameter. 



The "King Edward" was built in 1902, 9300 I.H.P., and the 

 diagram shows one of her L.P. turbines and reversing turbine in 

 one casing, to the same scale. 



In 1903 " The Queen," of 9000 I.H.P., commenced to ply between 

 Dover and Calais. The diagram shows one of her L.P. and reversing 

 turbines. 



In 1905 the Allan liners " Virginian " and " Victorian," of 12,000 

 I.H.P., went on service between Liverpool and Canada. The diagram 

 shows one of the L.P. and reversing turbines, which is 10 feet in 

 diameter and 35 feet in length ; and in last December the " Carmania," 

 of 30,000 tons displacement and 20,000 horse-power, commenced to 

 ply between Liverpool and New York. The diagram shows her L.P. 

 turbine, which is 14 feet in diameter. 



The application of the turbine to the propulsion of vessels involved 

 some interesting problems. The most important was, how slow could 

 a turbine be made to rotate consistently with the maintenance of its 

 efficiency in steam consumption, and at the same time be of moderate 

 weight and cost ? 



In the ^me problem naturally arose the question of how fast 

 could a screw-propeller be made to revolve when propelling a vessel 

 of a given size and at a given speed— in other words, when de- 

 livering a given propulsive horse-power at a given speed ? The first 

 question as to designing a low-speed turbine was solved in 1894 to 

 1896, by the aid of the accumulation of accurate data from experiments 

 on land turbines ; and the modification arrived at in tlie turbine has 

 been chiefly directed to the splitting of it up into two or three or 

 more turbines in series on the steam, and each Avorking a separate 

 shaft. This splitting up of the turbine results in a two-fold advan- 

 tage. It makes the turbine (which otherAvise would be very long) 

 much shorter, and because of being shorter finer clearances and less 

 loss ])y leakage results, and the whole engine is lightened. A 

 secondary gain, resulting from the division of the power over several 



