REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1903 175 



of sand, but it was soon discovered that the silica of the clay was 

 the only portion consumed in the process of manufacture, and a 

 good glass sand was substituted. The process of manufacture as 

 described by Mr Francis A. Fitzgerald in a lecture delivered 

 before the Franklin Institute on Dec. 11, 1896, is as follows :^ 



The crude materials for the manufacture of carborundum, viz, 

 sand, coke, sawdust and salt, are received in the stock building. 

 These are ready for immediate use, with the exception of the 

 coke, Avhich must be reduced to kernels of a certain size to be used 

 as " core '^ and ground to a fine powder to be used in making the 

 mixture or charge for the furnaces. To effect this, the coke is 

 first passed through a grinder, which breaks it up into small 

 pieces, and is then conveyed to the upper part of the building, 

 where it is passed successively through two cylindrical screens. 

 The first of these removes all particles of coke which are too 

 small to form the core, while the second allows kernels of the 

 requisite size to pass through its meshes and fall into the core 

 bin, conveniently situated as regards the other constituents of 

 the mixture. Below this bin are scales on which the sand, coke, 

 sawdust and salt are weighed out in proper proportions, and then 

 conveyed by an elevator to a mechanical mixer, from which the 

 mixture, ready for use, is emptied into a bin. The arrangement 

 of the machinery connected with all this work is such that it can 

 be attended to with ease by two men. 



The furnace room is built to accommodate 10 furnaces, though 

 at present there are but five. The furnaces are built of brick 

 and have the form of an oblong box, the internal dimensions being, 

 approximately, 16 feet in length, 5 feet in width and 5 feet in 

 depth. The ends are built up very solidly, with a thickness of 

 about 2 feet. In the center of either end are the terminals, con- 

 sisting of 60 carbon rods 30 inches long and 3 inches in diameter. 

 The outer ends of the carbons are inclosed in a square iron frame, 

 to which is screwed a stout plate, bored with 60 holes correspond- 

 ing to the ends of the carbon. Through each of these holes is 

 passed a short piece of % inch copper rod, fitting tightly in a hole 

 drilled in the carbon. Finally, all the free space between the 

 inside of the plate and the ends of the carbons is tightly packed 

 with graphite. Each plate is provided with four projections, to 

 which the cables conveying the current may be bolted. These 

 ends are the only permanent parts of the furnace ; the remainder, 

 which we shall now consider, is built up every time the furnace is 

 operated. 



^From notes of lecture published in pamphlet form by the Carborundum 

 Ck). 



