APPARATUS FOR THE ELECTRIC LIGHT. 133 



in a lathe, and therefore there are no occultations of the point of 

 maximum light like those produced by the projecting and com- 

 paratively cold corners of the retort-coke carbons. They are not 

 liable to the inconvenience of flying in pieces when first lighted, 

 as the others are, in consequence of the great and sudden ex- 

 pansion of the gas contained in their closed cellular spaces, 

 which are sometimes I cubic millimetre in capacity. By giving 

 them one and the same uniform density they are consumed by 

 the same amount for an equal section ; they are much better 

 conductors, and, without the addition of any substances other 

 than carbon, they are even more luminous in the proportion of 

 i 25 to i." 



The preparation preferred by Carre is a mixture of pow- 

 dered coke, calcined lamp black, and a syrup made of 30 

 parts of sugar and 12 parts of gum. The following formula 

 is given in his patent of the 151!! January, 1876 : 



Very pure coke, finely powdered ... ... 15 parts. 



Calcined lamp black 5 ., 



Syrup of sugar ... J to 8 



The whole is well pounded together, and from i to 3 

 parts of water are added to make up for the loss by evapora- 

 tion, and to give the required degree of consistence to the 

 paste. The coke is to be made with the best samples ground 

 -and purified by washing. The paste is then compressed and 

 passed through a draw-hole, and the carbons are afterwards 

 piled in crucibles and exposed for a certain length of time 

 to a high temperature. Details of the operations for prepar- 

 ing these carbons will be found at page 54 of H. Fontaine's 

 work. 



We may add that Carre, being desirous of imparting to 

 the electrical light the hues most suitable for theatrical pur- 

 poses, has succeeded in so treating his carbons that they 

 impart to the light a tint which, instead of being bluish- 

 white, has a rosy-yellow hue, that is very advantageous for 

 bringing out the complexions of the actresses. 



Carre's manufacture has, since the great experiments made 



