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



faster class of ships ; for cross-channel steamers it has found great 

 favour, and for Atlantic liners and ships of war it is being used to a 

 more and more considerable extent, and this tendency is not confined 

 alone to England, but is shown also on the Continent, and in the 

 United States and Japan. It will give a clearer idea of the subject 

 if we first of all examine more closely the characteristics of the steam 

 turbine, and generally how it works. 



All turbines derive their power from the impact of the steam, or, 

 more correctly speaking, from the momentum of the steam, flowing 

 through them, just as a windmill receives its power from the wind. 



There are three principal types of turbines now in general use, as 

 well as some which may be described as admixtures of these three 

 classes. They differ essentially in some respects, more particularly in 

 their methods of extracting the power from the steam. 



The first to receive commercial application, 1884, was the com- 

 pound or multiple expansion steam turbine ; the second was the De 

 Laval or single-bucket wheel, in 1888, driven by the expanding steam 

 jet ; and, lastly, the Curtis turbine, in 1896, which comprises some of 

 the principal features of the others combined with a sinuous treatment 

 of the steam. 



In the compound turbine, the steam is caused to flow through a 

 series of many turbine elements of gradually increasing size, graduated 

 so as to allow of the expansion of steam in small increments of volume 

 at each element, these increments of volume corresponding to the fall 

 of pressure necessary to cause the steam to flow through each element. 

 Each element consists of a row of guide blades and a row of moving 

 blades. The guide blades are attached in circumferential rows to the 

 case and project inwardly, and the moving blades are attached in 

 rows to a drum and project outwardly. The ends of the l)lades 

 throughout the turbine nearly touch the drum and case respectively. 



To form some idea of the forces at work in a turbine we should 

 consider, with approximate accuracy, that the steam flows through the 

 turbine with a force about ten times as great as that of the strongest 

 hurricane ; and though the force acting on each blade is small, perhaps 

 only a few ounces, or in the largest only a few pounds, yet in the 

 aggregate the force is great and can propel large ships or drive large 

 dynamos. 



The important factors upon which the proportions of the turbine 

 are based are the pressures, velocities and percentages of moisture in 

 the steam, as it gradually expands from turbine row to turbine row. 



The blades of the turbine are made of rolled and drawn brass, 

 well shaped, and polished so as to reduce the frictional losses in the 

 steam to a minimum. The steam enters all round the shaft and first 

 traverses the shortest blades on the smallest drum, then through 

 larger and larger blades set on larger and larger drums, and so on till 

 as it leaves the last blades it is expanded about 100-fold in volume. 

 At the opposite end to the blade drums are seen the balance pistons, 



