504 SCIENTIFIC RECORD FOR 1882 



volatilized. The vessel becomes filled with a blue gas similar to iodine 

 vapor, which deepens, becoming like indigo. The vapors condense on 

 the sides of the globe, making it opaque. The deposit resembles finely 

 divided carbon, but dissolves with effervescence in nitric acid. The lumi- 

 nous effect is more striking when copper electrodes are used. {Compfes 

 Eendvs^ xciv, pp. 1271, 1015; Fhil. 3Iag., July, Supplement, Y, xiii, p. 

 538.) 



Abdank has invented a new arc lamp, which was described by Preece 

 at the Southampton meeting of the British Association, in which the 

 regulating arrangement is separated from the lamp. The lower carbon 

 is fixed, the upper attached to a brass rod movable in the core of an 

 electro-magnet and lifted by a cUitch when the magnet is charged. The 

 magnet and carbon holder are fastened to the end of a rack, the pinion 

 of which is controlled by an electro-magnetic brake. The regulator i^ 

 differential in its action, and throws a shunted current on to the elec- 

 tro-magnet of the brake whenever the resistance between the carbons 

 becomes too great, thus allowing the carbons to approach. A cut-out 

 is attached, hy which the lamp is taken out of circuit when necessary. 

 {Nature, September, xxvi, p. 526.) 



In his address as chairman of the Council of the Society of Arts, Sie- 

 mens took for his subject electric lighting and the transmission of force 

 by electricity, considering the more practical side of the electrical ques- 

 tion. He made a calculation of the cost required to light the parish of St. 

 James, with its 30,000 people, 3,000 houses, and 784,000 square yards of 

 area, and concludes that an expenditure of 12 horse-power per house 

 would be required. The cost of the electricity he assumes to be in Lon- 

 don one shilling per 10,000 watts (;im])ere-volt8). Hence, to maintain 

 64,000 Swan lights it would cost £16 per hour. The total cost of the 

 plant he puts at £177,000. At the same rate the plant necessary for 

 the entire city would cost £14,000,000. The cost of each lamp per year 

 he estimates at 21s. 9JfZ. ; while the same light by gas at 2s. 8d. a thou- 

 sand feet would cost 20s. {Naiure, November, xxvn, p. 67.) 



In a lecture before the Eoyal Institution, Swan has discussed the 

 subject of incandescent lighting with special reference to its economy. 

 The great economy of high incandescence he strikingly illustrated by 

 passing through one of his lamps one unit of current. The light ob- 

 tained was equal to two candles. When one and a half units of cur- 

 rent was sent through the lamp, it gave thirty candles; so that for an 

 increase of current of one-half, involving a do\ibling of the energy ex- 

 pended, fifteen times the light was produced. In conjunction with Mr. 

 Stearn, in 1878, he reached the result that "when a well-formed carbon 

 filament is firmly connected with conducting wires and placed in a 

 hermetically sealed glass ball perfectly exhausted, the filament suf- 

 fers no apparent change even when heated to an extreme degree of 

 whiteness." "The first lamp having this elementary character (a simple 

 bulb pierced by two platinum wires supporting a filament of carbon) 



