1885.] KEW YORK ACADEMY OF SCIENCES. 101 



of arc lighting must ultimately give way before the incandescent 

 light, save for lai'ge spaces not requiring a close use of the eyes. 



The low potential, and lai-ger current of the incandescent 

 dynamos, render necessai'y a lower resistance in the conductors, 

 and so the cost of wiring for incandescent lamps is much greater 

 because of the increased weight of copper wire demanded to 

 convey the current without too great a loss in the form of lieat. 

 This is the pecuniary obstacle, and about the only one that pre- 

 vents the entire disappearance of the arc light before tlie incan- 

 descent light. Could an incandescent lamp be made of sufficiently 

 high resistance to enable the use of high potentials the hist ob- 

 jection to the system would vanish. Who knows but that in a 

 few days we may hear of its accomplishment ? 



The Edison 97 volt lamps in this test, outlived all the otliers ; 

 demanded the least weight of conductors, and was 13 per cent 

 less economical of power. It was the only lamp in the test that 

 justified a claim to 1000 hours of life. 



Nineteen out of twenty lamps entered by this company sur- 

 vived a continuous test of 1006 hours. 



Mr. Weston entered a tamidine carbon lamp, intended to be 

 used with 110^ volts, but imperfection of manufacture subse- 

 quently led him to pronounce them worthless. 



The more successful lamps were found to undergo a process 

 of gradual degradation which is attributable to two causes, an 

 increase of the resistance of the carbon fihiment, and a deposit 

 of carbon upon the interior of the glass of the lamp. 



The discoloration of the various lamps was carefully compared 

 after their life had ceased, and was remarkably deep in the case 

 of the Woodhouse & Eawson, and the Stanley 44 volt lamps. 

 Indeed, it would seem as if this discoloration was in some wise 

 proportional to the economy of the lamp, as tliese two were the 

 most economical of the maikes of lamps entered. 



A lamp may live a long time and yet be of little value for the 

 purpose of giving light, because of this degradation. If you 

 will take a lamp whicli has been used some time, and lay it upon 

 a white handkerchief, the gray coloring matter on the globe will 

 be brought out quite distinctly. 



Thus we see that great length of life with little usefulness 

 may be attained by lamps. Indeed, the Edison lamps, which 

 outlasted all others, had lost 36 per cent of their illuminating- 

 power at the end of 1006 hours. 



Before turning to my last head, I will remind you that the 

 direct conversion of heat into electrical energy by Clamond's 

 stoves only produced 26 candle power per pound of coke, as 

 against 40 candles per pound of anthracite in the usual way 

 with incandescent lamps. 



