632 SCIENTIFIC RECOED FOR 1885. 



which in the lamps examiued is about 28-7, is nearly the potential dif- 

 ference at which the lamps begin to emit light. Hence the law may be 

 stated as follows : The effective potential difference varies as the cube 

 root of the efficiency. {Phil. Mag., May, 1885, V, Xix, 368; Nature^ 

 April, 1885, xxxi, 522.) 



Fleming has further studied the phenomenon of molecular shadows 

 in Edison incandescent lamps. In his earlier experiments he suggested 

 the similarity of the phenomenon in question to those observed in high 

 vacua by Orookes, the surface of the glass being coated with a deposit 

 of carbon, with the exception of a clear line marking the intersection of 

 the glass with the plane of the loop, and being in fact a shadow of the 

 loop, apparently caused by the emission of matter from the terminals. 

 The author has now succeeded in producing this phenomenon at will by 

 passing a very strong current momentarily through a lamp, and has 

 produced similar deposits of various metals used as electrodes. These 

 deposits show colors by transmitted light, and, as a general result, he 

 concludes that red metals, such a gold and copper, appear green by 

 transmitted light, whereas white metals, like silver and platinum, ap- 

 pear brown. This result is obviously of the same character as that ob- 

 tained by Wright.— J.W. J. ScL, 1877, III, xiii, 49 ; xiv, 169. {Phil. 

 Mag., August, 1885, V, XX, 141; Nature, July, 1885, XXXII, 263; Am. 

 J. Sci., October, 1885, III, xxx, 314.) 



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