2 20 POPULAR SCIENCE MONTHLY. 



force will more and more exclude lieat from the chain of trans- 

 formations which issue in the locomotive's flight, in the whirl of 

 factory and mill; and thus in some degree is allayed the fear, 

 never well grounded, that when the coal fields of the world are 

 spent, civilization must collapse. As the electrician hears this 

 foreboding, he recalls how much fuel is wasted in converting heat 

 into electricity. He looks beyond either turbine or shaft turned 

 by wind or tide, and, remembering that the zinc dissolved in his 

 battery yields at his will its full content of energy, either as heat 

 or electricity, he asks. Why may not coal and forest tree, which 

 are but other kinds of fuel, be made to do the same ? 



In another field let us observe electricity as a factor of fruit- 

 f Illness quite as singular. It was at first the chemist who eman- 

 cipated electricity for new and myriad uses. His successor to-day 

 is the engineer, who wins his spurs by bringing his generator to 

 practical perfection, by improving his steam and gas engines to 

 double their efficiency of thirty years ago. If to the engineer and 

 mechanic the electric art owes much, magnificently has the debt 

 been repaid. As we discover in replacing at our street door an 

 old-fashioned moving bell pull by an electric wire armed with a 

 push button, electricity transmits motion without movement of 

 its conductor as a mass. Availing himself of this golden property, 

 the machinist removes from his shop a labyrinth of wheels and 

 belts and puts in their stead a few wires at rest, each in charge 

 of the motor actuating a machine. Manifold gains result. The 

 power needed to whirl these wheels and belts is saved, and when 

 but one or two machines of a large number are to be set in motion 

 the economy rises to a high figure, while the workshop is lighter, 

 cleaner, more wholesome in every way. Since electricity is of all 

 phases of energy the easiest to preserve from losses resembling 

 leakage or friction, the current can not only be distributed 

 throughout the largest workshop with convenience and economy, 

 it can be sent to the shop from an engine or a water wheel many 

 miles away, as in connecting motors at Buffalo to dynamos at 

 Niagara, twenty-seven miles distant. With the transmission of 

 electricity for distances vastly exceeding twenty-seven miles we 

 have long been familiar in the telegraph. It is by improving the 

 coverings which prevent the current escaping from its wire, by 

 taking advantage of the fact that a wire can almost as well carry 

 a current of high tension as of low, and, above all, by increasing 

 the quantity of the current so as to make the enterprise worth 

 while, that the telegraphy of power has followed upon the teleg- 

 raphy of mere signals. 



In the telegraph at work over long distances a remarkable 

 peculiarity of electricity displays itself. In days of yore, when 

 letters were intrusted to a chain of messengers, each of whom bore 



