APPARATUS FOR THE ELECTRIC LIGHT. 



137 



2. That lime, magnesia, and strontia increased the light in 

 the proportion of 1*30 or 1-50 to i, giving it different colours ; 



3. That iron and antimony brought up the increase to 

 i*6o and 170; 



4. That boric acid increased the duration of the carbons 

 by covering them with a glassy coating which protected them 

 from the air, but without increasing the light ; 



5. That the impregnation of pure and regularly porous 

 carbons by solutions of various substances is a convenient 

 and economical means of producing their spectra, but it is 

 preferable to mix the elementary substances with compound 

 -carbons. 



Metallized Carbons. According to E. Reynier, the 

 carbons being consumed a little by combustion on their 

 lateral surfaces, which glow for a length of 7 or 8 millimetres 

 above and below the luminous point, there is a complete loss 

 as regards the light, and it would be an advantage to cover 

 them with a metallic covering in order to avoid this lateral 

 combustion. It follows, in fact, from his experiments in the 

 workshops of Sautter and Lemonnier with a Gramme machine 

 of the 1876 form, that the metallized carbons are consumed 

 less than the ordinary carbons, as the following results show: 



