SOMK NKW MODES OK LUillTlNG. 271 



Xcw methods of electric luihthuj. — As early as LSTS Arclicrcaii, 

 Carre, and Oauduin s()ii<j:lit to au<^m'ii( llu' luminosity of the electric 

 arc by rendering the arc itself as well as the positive carbon incandes- 

 cent. For this purpose they mixed with the carbon of the electrodes 

 suitable substances such as oxides of calcium or ma<rnesiuui; l)ut 

 unfortunately there occurred a preci})itation of the I'efractory oxides 

 upon the lower carbon, and a formation of scoria which resulted in a 

 prejndicial unsteadiness for illumination. After the Welsbacli man- 

 tle attained success, new efforts were made to apply this })rinciple of 

 incandescence of the arc, and Monsieur Bremer exhibited at the expo- 

 sition of 1000 a model having four special carbons, and in which the 

 light produced in the arc was reflected downward. The presence of 

 mineral matter resulted in increasing the luminous surface, modifying 

 the color of the light as desired, and in diminishing by one-half the 

 current consumption for a given illumination. 



A considerable number of concerns, notably in (lermany, are now 

 producing flaming arc lamps more or less patterned after that of 

 Bremer. The [)rincipal differences consist in the varied construc- 

 tion of the electrodes, but all are composed of mixtures of carbon 

 and some salt of calcium, usually fluorspar. Professor Wedding, 

 having studied the influence of this substance on the consiunption 

 of energy in the lamp, has found that the most favorable conditions 

 are found with 15 per cent fluorspar. Electrodes of this composi- 

 tion are found to consume but 0.15 watts per candle, as compared 

 with 0.5 watts for the ordinary arc. 



Doctor Arndt's researches at the Technische Hochschule in Berlin 

 have shown that the operation of the flaming arc does not involve 

 any ajjpreciable production of <)l)jectionable gases. Furthermore, 

 the light produced is of a yellowish-red color and much less cold and 

 harsh than that of the ordinary arc. It more resembles sunlight in 

 color, and ])enetrates better through fog than the light of shorter 

 wave length produced by the ordinary arc. 



The Bremer arc recjuires the use of si)ecial lamps, but by emplov- 

 ing trizonal carbons A. Blondel has avoided this iiiconxenience. 

 Minerals are contained in the two interior zones, and such arcs, con- 

 suming only 3 amperes, have been found to give nearly three, and 

 similar arcs, consuming 9 amperes, more than four, times the effi- 

 ciency of the ordinary arc light consuming equal energy. 



In the same general category belongs the lamp with three elec- 

 trodes and two arcs, devised by L. Sigfried Andersson, of Stockholm. 

 For the purpf)se of increasing the area of luminous surface, and at 

 the same time producing incandescence within the arc, there is 

 introduced between the two carbons which carry the current a third 

 cylinder, formed of a more refractory substance than the two others. 

 The regulation of this lamp is very delicate, and is effected in a most 



