132 ELECTRIC LIGHTING. 



black is collected. Any obstruction in the retort is removed by 

 means of a scraper. From the last receiver which forms the 

 second branch of the inverted u, a curved pipe leads the hydro- 

 gen gas and the undecomposed volatile products under a grating." 



Unfortunately this process was very incomplete, and offered 

 no security for the quality of the products. Along with ex- 

 cellent carbons giving very satisfactory results there were 

 others very bad, and sometimes even worse than those ob- 

 tained from retort-coke. Therefore Carre determined to 

 study the problem afresh, and he thus speaks of it in the 

 Comptes rendus de r Academic des Sciences of the igth February, 

 1877, P- 346: 



Carres Method. "The superiority for various experi- 

 ments of artificial carbons, and the possibility of purifying by 

 alkalis, acids, aqua-regia, &c., the carbonaceous powders 

 that enter into their composition, then led me to seek for 

 some means of producing them economically. By moisten- 

 ing the powders either with syrups of gum, gelatine, &c., or 

 with fixed oils thickened with resins, I succeeded in form- 

 ing pastes sufficiently plastic and consistent to be forced into 

 cylindrical rods through a draw-plate placed at the bottom of a 

 powerful compression apparatus under the pressure of about 

 100 atmospheres. Carbons are now manufactured by this 

 process, and 1 have at various times presented some of them 

 to the Academic des Sciences and to the Societe a"* encouragement. 



" These carbons have three or four times the tenacity and are 

 much more rigid than retort-coke carbons, and cylinders of 10 

 millimetres diameter may be used of a length of 50 centimetres 

 without any danger of their bending or crossing during the breaks 

 of the circuit, which often happens with others. They may 

 be as easily obtained of the slenderest diameters (2 millimetres) 

 as of the largest. 



" Their chemical and physical homogeneity g;ives great steadi- 

 ness to the luminous arc ; their cylindrical form, combined with 

 the regularity of their composition and structure, causes their 

 cones to continue as perfectly shaped as if they had been turned 



