THE CONQUEST OF NATURE 



against its blades. The tiny windmills which children 

 often make by twisting pieces of paper illustrate the 

 same principle. Of course, in its developed form the 

 turbine is somewhat elaborated, in the aim to utilize as 

 large a proportion of the energy of the falling water 

 as is possible ; but the principle remains the same. 



The turbine wheel was invented by a Frenchman 

 named Fourneyron, about three-quarters of a century 

 ago (1827), but its great popularity, in America in 

 particular, is a matter of the last twenty or thirty years. 

 To-day it has virtually supplanted every other type 

 of water wheel. To use any other is indeed a wasteful 

 extravagance, as the perfected turbine makes available 

 more than eighty per cent, of the kinetic energy of any 

 mass of falling water. A turbine wheel two feet in 

 diameter is able to do the work of an enormous wheel 

 of the old type. 



Turbine wheels are of several types, one operating 

 in a closed tube to which air has no access, and another 

 in an open space in the presence of air. The water 

 may also be made to enter the turbine at the side or from 

 below, thus serving to support the weight of the mech- 

 anism a consideration of great importance in the case 

 of such gigantic turbines as those that are employed 

 at Niagara Falls, which we shall have occasion to 

 examine in detail in a later chapter. 



The power generated by a revolution of the turbine 

 wheel may, of course, be utilized directly by belts or 

 gearings attached to its axle, or it may be transferred 

 to a distance, with the aid of a dynamo generating 

 electricity. The latter possibility, which has only re- 



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