632 SCIENTIFIC RECORD FOR 1885. 



which in the lamps examined 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 varieu as the cabe 

 root of the efficiency. {Phil. Mag., May, 1885, V, iix, 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 Crookes, the surface of the glass being coated with a deposit 

 of carbon, with the exception of a clear bne 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 resulr, he 

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

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

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

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

 Mag., August, 1885, V, XX, 141 ; Nattire, July, 1885, xxxii, 263 ; Am. 

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



BIBLIOGRAPHY OF PHYSICS, 1885. 



Practical Physics. R. T. Glazebrook and W. N. Shavr. 16mo. pp.,xxii, 487. Lon- 

 don and New York, 1885. 



Lessons in Elementary Practical Physics. Balfonr Stewart and W. W. H. Gee. Vol. 

 I. General Physical Processes. 16nio. pp. xvi, 298. London, 1885. (Macmil- 

 lan.) 



Properties of Matter. P. G. Tait. 16mo. pp. viii, 320. Edinburgh, 1885. (Black.) 



Mathematical and Physical Papers. Prof. Sir Wm. Thomson. Vol. II. 8vo. Cam- 

 bridge University Press, 1884. 



Outlinesof Natural Philosophy. J.D.Everett. 12mo. London, 1885. (Blackie.) 



Corso di fisica applicata. G. Grassi. 8vo. pp. 5Q0. Napoli, 1884. (Pellerano.) 



Elementi di fisica e meccanica applicata alia nautica. Meteorologia e geografia lisica 

 del mare. E. M. Russo. 2 vols. 8vo. pp. 624, 591. Napoli, 1884. (Pellerano.) 



Physical Arithmetic. A. Macfarlane. 8vo. pp. 354. London, 1885. (Macmillan.) 



Grundziige der Molecular-Physik und der mathematischen Chemie. W. C. Wittwer. 

 8vo. pp. vii, 198. Stuttgart, 1885, 



Ueber den Begrift" der Kraft mit Beriicksichtigung des Gesetzes vou der Erhaltung der 

 Kraft. E. Dreher. 8vo. Berlin, 1885. 



Histoire des sciences math^matiques et physiques. M. Marie. 8vo. pp. 264. Paris, 

 1885. ( Gauthier-Villars. ) 



Syllabus of a Hundred Physical Measurements. H. Whiting. 12mo. Cambridge, 

 1885. (Wheeler.) 



Problfemes de physique avec leurs solutions d^velopp^es. A. F. Chevallier et A. 

 Mueutz. 2d ed. 8vo. pp. viii, 205. Paris, 1885. 



