THE DURATION OF HUMAN LIFE. 



95 



6. The cost of the copper wire, reckoned at eight pence per pound, 

 is 37,000 ; the interest on which at five per cent, is 1,900 a year. 

 If 5,250 horse-power at the Niagara end costs more than 1,900 a 

 year, it would be better economy to put more copper into the con- 

 ductor ; if less, less. I say no more on this point at present, as the 

 economy of copper for electric conduction will be the subject of a 

 special communication to the section. 



I shall only say, in conclusion, that one great difficulty in the way 

 of economizing the electrical transmitting power to great distances (or 

 even to moderate distances of a few kilometres) is now overcome by 

 Faure's splendid invention. High potential, as Siemens, I believe, 

 first pointed out, is the essential for good dynamical economy in the 

 electric transmission of power. But what are we to do with 80,000 

 volts when we have them at the civilized end of the wire ? Imagine a 

 domestic servant going to dust an electric lamp with 80,000 volts on 

 one of its metals ! Nothing above 200 volts ought on any account 

 ever to be admitted into a house or ship or other place where safe- 

 guards against accident can not be made absolutely and for ever trust- 

 worthy against all possibility of accident. In an electric workshop 

 80,000 volts is no more dangerous than a circular saw. Till I learned 

 Faure's invention I could but think of step-down dynamos, at a main 

 receiving-station, to take energy direct from the electric main with its 

 80,000 volts, and supply it by secondary 200 volt dynamos or 100 volt 

 dynamos, through proper distributing wires, to the houses and factories 

 and shops where it is to be used for electric lighting, and sewing- 

 machines, and lathes, and lifts, or whatever other mechanism wants 

 driving power. Now the thing is to be done much more economically, 

 I hope, and certainly with much greater simplicity and regularity, by 

 keeping a Faure battery of 40,000 cells always being charged direct 

 from the electric main, and applying a methodical system of removing 

 sets of fifty, and placing them on the town-supply circuits, while other 

 sets of fifty are being regularly introduced into the great battery that 

 is being charged, so as to keep its number always within fifty of the 

 proper number, which would be about 40,000 if the potential at the 

 emitting end of the main is 80,000 volts. 



-- 



THE DURATION OF HUMAN LIFE. 



By M. DE SOLAVILLE. 



CAN man reach and pass the age of a hundred years ? is a question 

 concerning which physiologists have different opinions. Buffon 

 was the first one in France to raise the question of the extreme limit 

 of human life. In his opinion, man, becoming adult at sixteen, ought 



