170 TRANSACTIONS OF THE CANADIAN INSTITUTE. —~ [VoL. VIII. 
The history of carborundum, may well be likened to that of carbide, its 
discovery being accidental. Mr. E. C. Acheson, whose patents are em- 
ployed in this industry, was endeavouring to obtain crystals of carbon by 
melting together clay and carbon, the latter of which it was hoped might 
crystallize from the resulting reduced aluminum. Hard crystals were 
found after the fused mass had cooled, the component parts of which were 
concluded to be carbon and aluminum, and for which he invented the 
name ‘‘carborundum.’’ Analysis, however, proved the new substance 
to contain silicon and carbon, and only a small quantity of alumina. 
Further experiments were made with mixtures of sand, carbon and salt 
as a fluxing agent, and large crystalline masses of carborundum were ob- 
tained. The substance thus formed corresponds to the formula CSi, is 
extremely hard, and is used in place of emery and corundum. In the 
manufacturing process the materials employed are sand, coke, salt, and 
sawdust; the coke is reduced to kernels of a certain size, to be used for 
making the ‘‘core,’’ and other portions are ground to a fine powder for 
mixing with the charge of sand and salt. The original form of furnace 
was fitted with a pair of carbon terminals, which could be moved longitud- 
inally, and was essentially an are furnace, the chemical changes taking 
place being due to the high temperature of the arc passing between the 
carbon terminals. In 1895 this form was abandoned and a continuous 
electrical connection made between the terminals by the introduction of a 
‘core’ of granulated coke. By regulating the diameter of the core it 
could be heated to a sufficiently high temperature to convert the surround- 
ing mixtures into carborundum. In the modern form of furnace the brick 
ends and carbon electrodes, with the necessary terminals for connecting 
up the current, are the only permanent portions. The charge, consisting 
of sand, finely-ground coke, and sawdust,—added to render the mixture 
more porous and consequently allow the gaseous products to pass through 
the mass—is placed in the furnace till it is on a level with the lower edge 
of the carbon electrodes. ‘The coke ‘‘core ’’ is then filled in, made into 
cylindrical form by hand, and finally surrounded at its sides and on the 
top by the remainder of the charge. Care is taken to prevent the mixture 
coming in contact with the carbon terminals, and necessary retaining walls 
are built up of bricks as the charging operation is proceeded with. The 
current is passed for thirty-six hours, and after cooling, the walls are taken 
down, unused ‘‘charge”’ raked off, and the outer crust of carborundum 
exposed. A cross section of the contents of the furnace presents many 
interesting characteristics. In the centre is the core, which has been, to a 
large extent, converted into amorphous carbon and graphite. From this 
there radiate beautifully coloured carborundum crystals to a distance 
of from ten to twelve inches. Next a thin inner crust of amorphous car- 
borundum of a light green colour is met with, then the outer crust, also 
