PHYSICS. 619 



directly to the substance to be melted. (Ann. Chem. Phys., December, 

 ' 1883, V, xxx, 4G5; J. Phys., Marcli, 1883, II, n, 124.) 



Dobrohoff-Maikoff has devised a form of arc-lamp, in which a coil of 

 coarse wire surrounds an iron tube, within which is a rod of iron. 

 When the current passes the two are similarly magnetized, and the rod 

 is repelled from the tube. By means of articulated levers this motion 

 is made to regulate the distance of the carbons. (J. Phys., December, 

 1883, II, ii, 571.) 



Lever has invented a simplified form of clutch arc-lamp, in which the 

 upper carbon is clamped in a brass holder sliding freely vertically. A 

 brass washer or collar fits accurately but loosely to it, supported on one 

 side by an adjustable screw, and on the other by a metal piece attached 

 to the framework. This framework is supported by a spiral spring, 

 which keeps the washer tilted against the carbon-holder. This spring 

 is antagonized by an electromagnet in shunt circuit, so that when the 

 current is turned ou, the carbon is allowed to fall until contact takes 

 place. Then the shunt magnet loses its force and the spring separates 

 the carbons to form the arc. (Nature, January, 1883, xxvn, 274.) 



Williams has claimed for an American, Starr, the invention of the in- 

 candescent lamp, which was patented after his death by King, in 1845. 

 It consisted of " a short stick of gas retort carbon" in a barometric 

 vacuum. " The light was far more brilliant and the carbon stick more 

 durable than the flimsy threads of the incandescent lainps now in use." 

 It was abandoned solely on account of the cost of suppljing the power. 

 (Nature, January, 1883, xxvn, 241.) 



Fleming has called attention to a jhenomenon of molecular radiation 

 in the Edison lainp. When a loose contact occurs so that an arc is 

 formed and the copper projected on the walls of the glass, there is a 

 shadow of one side of the loop on the glass where this side of the fila- 

 ment has protected the glass from the copper bombardment. (Phil. 

 Mag., July, 1883, V, xvi, 48.) 



Hopkinson has delivered a lecture at the Institution of Civil Engi- 

 neers on " some points in electric lighting." The building was lighted 

 by about 230 Edison lamps, each of 10 candles, and each requiring 75 

 watts of power. To produce the same lG-candles light in ordinary good 

 flat flame gas-burners would require between 7 and 8 cubic feet of gas 

 per hour, contributing heat to the atmosphere at the rate of 3,400.000 

 foot-pounds per hour, equivalent to 1,250 watts, or nearly seventeen 

 times as much heat as the incandescent lamp of equal power. The di- 

 rection of progress was in the improvement of the lamp. (Nature, 

 April, 1883, xxvn, 592.) 



Geraldy has published some valuable statistics comparing the cost of 

 the electric arc-light with gas, both as to its actual cost and its cost per 

 candle power. (Nature, October, 1883, xxviii, 025.) 



Tommasi has contrived an electric-light regulator in which the vary- 

 ing resistance which selenium has when exposed to light is made use of. 



