Applied Science 813 



of the jet. The most remarkable Pelton Wheel plant is probably 

 that at Fully, Switzerland. Water is here led downwards from 

 a lake through a pipe three miles long, which in its short course 

 sinks more than a mile say, through six times the height of the 

 Eiffel Tower so that at the lower end the pressure in the pipe 

 exceeds a ton per square inch! The water leaves the nozzle at 

 a speed of nearly 400 miles per hour, and, though the wheels 

 are 12 feet in diameter, revolves them 500 times per minute. It 

 may be mentioned in passing that the resistance offered by 

 rapidly moving water to any attempt to deflect its course is 

 remarkable. A jet 3 inches in diameter emerging under a 

 pressure of 500 Ib. per square inch cannot be cut through by a 

 blow with a crowbar. 



Steam Turbines 



In steam-operated power-stations, where the larger part 

 of the electrical energy used by man is still generated, the steam 

 turbine, coupled direct to a generator, is the counterpart of the 

 water turbine. 



A steam turbine of the Parsons type consists of a long closed 

 horizontal drum mounted on a shaft in a strong casing, through 

 the ends of which the shaft passes. The annular clearance space 

 between the drum and casing increases by stages, as the latter 

 is "stepped," and this space is filled by rows of curved blades, 

 alternate rows being attached to the drum, and those between 

 them to the casing. The tips of the drum blades just do not 

 touch the casing; while those on the casing just clear the drum 

 and the other blades. In a large turbine there may be some hun- 

 dreds of thousands of blades, of lengths ranging from an inch 

 to over a foot. Steam is admitted at the smaller end of the casing 

 and threads its way through the many rows of guide and moving 

 blades, every one of the last getting a sideways push which is 

 transmitted through drum and shaft to the generator. After 

 expanding greatly the steam escapes to the condenser either 



