UTILIZING THE SUN'S ENERGY. 265 



fully utilized, something like 200,000,000 horsepower. Niagara, at the 

 falls alone, can supply between 4,000,000 and 5,000,000, and a consid- 

 erable additional quantity from the rapids above and below the falls, 

 and numerous other water powers distributed over the hilly and moun- 

 tainous portions of the country will in time no doubt become centers 

 of power production and distribution. The one threatening aspect of 

 the hydraulic power problem is the extreme probability that the con- 

 tinued destruction of forests and vegetation will make the streams 

 more and more unreliable for continuous supply. 



Wind power is another source of available energy, like water power, 

 deriving its origin from the energy of the sun's rays, which may, as 

 time goes on, provide a continually larger amount of utilizable energy 

 for the use of mankind; but it is subject even in greater degree than 

 water power to the objection that it is variable and unreliable for steady 

 work. The winds are continually rising and falling. "As variable as 

 the winds" well indicates the uncertainty^ of atmospheric currents as 

 a source of power for industrial purposes. Rising to a gale and fall- 

 ing to a calm, alternately, the portion of the time during which this 

 power is actually available is small, and, still worse, its available periods 

 are as likely to come at unsuitable hours and seasons as when wanted. 

 There is ample wind power for all purposes, undoubtedly, could it be 

 regulated, stored, and economically availed of; but while no one can 

 say what ma} 7 or may not be accomplished by the coming inventor, 

 mechanic, and engineer, it does not seem likety that this particular 

 problem will be successfully solved even under the stimulus of van- 

 ishing fuel supplies. 



Tidal power is still another possible source of industrial energy, and 

 one which also has its own and peculiar difficulties of utilization. It 

 is a regular and well-measured and well-known quantity; its hours of 

 rise and fall, and the heights of rise and fall are well established. But 

 when it is sought to design a system of utilization that shall be cheap, 

 practicable, reliable, and compact — one that may compete with other 

 power systems — it is found to be a very difficult and for the time at 

 least impracticable system of power production. 



At the moment, engineers and men of science are studying the art 

 of reducing to harness the direct rays of the sun, and the solar engine 

 is exciting special interest. It is no novelt}% and many inventors have, 

 for years past, worked upon this attractive problem; but probably at 

 no time in the past has this matter assumed importance to so many 

 thoughtful and intelligent men or excited so much general interest. 

 John Ericsson, the great inventor and mechanic, when writing, in 

 1876, the great quarto volume which he intended should be the memorial 

 of his life's work, devoted a very large proportion of its space to the 

 account of his solar engines and of the scientific investigations made 

 in the course of his work for the purpose of ascertaining the amount 



