CH. II] DARK-GROUND ILLUMINATION WITH HIGH POWERS ;6k 



"Pointolite" lamp for direct current. Developed by E. A. Gimingham and 

 S. R. Milliard at the Edison Swan Elect. Co., Ltd. Ponders End, Middle- 

 sex, England. This is a tungsten enclosed arc for direct current. It yields 

 about 500 candlepower, and has a life of 500 hours. See Trans. Inst. Elect. 

 Engineers, Vol. LIV, 1916, p. 15; Illuminating Engineer, Vol. II, p. 324, 

 1919; Chem. and Metallurgical Enginering, Vol. XXII, 1920, p. 281. 

 SPITTA, E. J. Microscopy, the construction, theory and use of the microscope 



(1907). 



WENHAM, F. H. (Dark-field Illumination.) Trans. Micr. Soc. London, Vol. Ill, 

 1850, pp. 83-90; Quart. Jour. Micr. Sci., Vol. II, 1854, pp. 145-158; Trans. 

 Micr. Soc., London, in Quart. Jour. Micr. Sci., Vol. IV, 1856, pp. 55-60. 

 WRIGHT, SIR A. E. The Principles of microscopy (1907). 



