296 THE POPULAR SCIENCE MONTHLY. 



course the " Waste Forces of Nature," to which I now invite your 

 attention. 



Of these, the first to be named, from the magnitude of the possi- 

 bilities that advanced thinkers have attached to it, is that fountain of 

 all terrestrial energy, our sun. 



To introduce this topic properly, I beg to remind you at the outset 

 that the progress of science during the last half century has been 

 most pronounced and satisfactory in the investigation of the nature, 

 origin, interdependence, and interconvertibility of the various mani- 

 festations of energy that are called familiarly " the forces of na- 

 ture" ; and among the most philosophical generalizations that the 

 science of our times may boast of having established is the demonstra- 

 tion, upon the most complete and satisfactory experimental evidence, 

 that every manifestation of terrestrial activity has more or less direct- 

 ly a solar origin. Every exhibition of force, physical or chemical, 

 inorganic or vital, the multifarious consequences connected with the 

 circulation of air and water over the surface of the earth, and in her 

 oceans, and which involve the causation of the winds, aerial and 

 aqueous currents, and rainfall, and the effects of these commonplace 

 but vastly important phenomena in establishing and maintaining those 

 climatic conditions upon which the existence of life upon the earth is 

 absolutely dependent, are directly referable to the forces of solar ra- 

 diation. Ay, there is good reason for the belief, which is entertained 

 by most competent and eminent authorities, that the periodical recur- 

 rence of famines and pestilences and other scourges that afflict man- 

 kind, and which the superstitious of all ages are wont to ascribe to 

 the anger of an offended deity, coincides with the periodical maxima 

 and minima in the intensity of the solar emanations that reach the 

 earth ; and that even such apparently disconnected and arbitrary 

 things as the social and political affairs of mankind, which are intimate- 

 ly bound up with the successful pursuit of agriculture and commerce, 

 are therefore demonstrably under the direct and immediate dominion 

 of the solar rays. 



But, to return from a digression that is only of incidental interest 

 to us here, I desire you to conceive of the amazing fact that the stu- 

 pendous aggregate of terrestrial activity is derived from that infinites- 

 imal fraction only of the solar emanations that is intercepted by the 

 earth a fraction less than the two-billionth part of the sum total of 

 energy that he is unceasingly radiating into space ; and it is my imme- 

 diate purpose here to invite your attention to the interesting question 

 whether it is within human reach to convert a portion of the measure- 

 less floods of power that the sun pours out upon the earth into me- 

 chanical energy, or into other forms in which it will be more directly 

 available for useful purposes. 



The proposition here announced, I must advise you, is not the 

 visionary notion of impracticable theorists, but is one that, on the con- 



