to: 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



latter is disintegrated simultaneously with the formation of a column of 

 Light and of an induction track for the current, which continues after 

 the return of the mercury into its original position. The inconvenience 

 of the long tube may be reduced by adopting a U -shape, which not only 

 reduces the length to one-half, but is found to facilitate the starting 

 and to enlarge the illuminated area. This shape is also more convenient 

 for application to various parts of the human body. Several of these 

 lamps may be electrically joined side by side, above or below, or in such 

 ways as may be found desirable. The spectrum of the uviol lamp is 

 exceedingly rich in lines, and extends down to wave-length 253. The 

 specific intensity of the visible radiation fluctuates between 0*31 and 4 - 3 

 Hefner candles per sq. cm. according to the dimensions of the lamp. It 

 follows that the uviol-lamp is an extremely advantageous means of 

 converting electrical energy into effective radiating energy of short 

 wave-length. It is likely to be useful not only in photography but in 

 many chemical investigations, and in certain skin diseases. It has a 

 deadly effect on bacteria and minute living organisms, as well as on the 

 smaller species of insects. Under a lamp suspended during a summer 

 night in a room with windows opened, thousands of dead insects were 

 swept up the following morning. 



Beck's Eyeshade. — This eyeshade (fig. 172), to obscure the un- 

 employed eye in monocular Microscopes, is specially adapted for Beck"s 

 instruments. 



Fig. 172. 



Abbe Camera Lucida. — This camera lucida (fig. 173) is a cheap 

 form of the Abbe Camera Lucida, and has a cubical prism which is 



Fig. 173. 



provided with a series of rotating tinted glasses. The holder carrying 

 the prism and tinted glasses can be thrown on one side on a pivoted 



