290 THE POPULAR SCIENCE MONTHLY. 



of living force and its preservation, but he does so for the most part 

 quite mechanically, so that he appears to think no more about it than 

 the beaver when he builds his hut. Man also does most things long 

 before he understands them, and this is part of his nature. If he 

 could make use of things only after having thoroughly investigated 

 them, his life would be a poor one, and barely possible. If we had to 

 study the functions of our clothing and its material before we could 

 put it on, we should be frozen to death long before, and no carrier 

 would have attempted to horse his cart before the time of Galileo and 

 Newton, 



Here I find myself drawing a dangerous parallel. You may ask 

 me at once whether I believe a carrier will be a better carrier for un- 

 derstanding the laws of motion, and whether our clothing and our 

 dwellings will one day be superior to what they are now, because we 

 shall then have learned to understand their functions better. I leave 

 the answer to the future with the utmost confidence. The experience 

 of the past sets me completely at ease. At all times and everywhere 

 it has been the case that each progress in the recognition of laws, that 

 each new fact established, and each new method applied by science, 

 each new way on which science has directed us, has finally had its 

 practical and useful consequences. Excuse me if I continue to dwell 

 on this favorite subject of mine. 



What men call useful is quite a relative term ; they call a thing so 

 as soon as they find out what use they can make of it. Of course, a 

 thing must exist before we recognize it, and we must become aware 

 of certain of its properties and relations before we can make use of 

 them for any practical purpose. Certainly the recognition of the laws 

 of motion by Galileo, Kepler, Newton, Laplace, and others, has not 

 brought about a revolution, or made a sensation among the carriers, 

 but from these recognized laws sprang and were evolved new ideas, 

 purified from the gross pi-imitive slag, and they led on to the railway, 

 etc. Other examples demonstrate still more clearly the connection 

 betAveen theory and practice. 



Electric telegraphy, which is not only practical and useful, but al- 

 ready indispensable to us, had its first origin in the observations of 

 the anatomist Galvani, who saw the legs of frogs quiver when they 

 came in contact with different metals. Imagine to yourself great 

 practical men of the time, whether statesmen, or divines, or soldiers, 

 or physicians, witnessing Galvani's experiments going on year after 

 year ; certainly every one of them would have thought that the man 

 could apply himself to something more useful. But from that form 

 of electricity which Galvani detected there sj^rung the researches and 

 works of Volta, Summering, Stcinheil, Morse, and Wheatstone, to 

 whom we owe the whole of our telegraphic system. Place together 

 in your mind the quivering leg of the frog and the transatlantic cable. 



After the- discovery of Columbus the Spaniards found in the sand 



