Besides its use in combining and separating different elements the electric furnace is able to change a single element into its various forms.  Carbon, for instance, is found in three very distinct forms:  in hard, transparent and colorless crystals as the diamond, in black, opaque, metallic scales as graphite, and in shapeless masses and powder as charcoal, coke, lampblack, and the like.  In the intense heat of the electric arc these forms are convertible one into the other according to the conditions.  Since the third form is the cheapest the object is to change it into one of the other two.  Graphite, plumbago or “blacklead,” as it is still sometimes called, is not found in many places and more rarely found pure.  The supply was not equal to the demand until Acheson worked out the process of making it by packing powdered anthracite between the electrodes of his furnace.  In this way graphite can be cheaply produced in any desired quantity and quality.

Since graphite is infusible and incombustible except at exceedingly high temperatures, it is extensively used for crucibles and electrodes.  These electrodes are made in all sizes for the various forms of electric lamps and furnaces from rods one-sixteenth of an inch in diameter to bars a foot thick and six feet long.  It is graphite mixed with fine clay to give it the desired degree of hardness that forms the filling of our “lead” pencils.  Finely ground and flocculent graphite treated with tannin may be held in suspension in liquids and even pass through filter-paper.  The mixture with water is sold under the name of “aquadag,” with oil as “oildag” and with grease as “gredag,” for lubrication.  The smooth, slippery scales of graphite in suspension slide over each other easily and keep the bearings from rubbing against each other.

The other and more difficult metamorphosis of carbon, the transformation of charcoal into diamond, was successfully accomplished by Moissan in 1894.  Henri Moissan was a toxicologist, that is to say, a Professor of Poisoning, in the Paris School of Pharmacy, who took to experimenting with the electric furnace in his leisure hours and did more to demonstrate its possibilities than any other man.  With it he isolated fluorine, most active of the elements, and he prepared for the first time in their purity many of the rare metals that have since found industrial employment.  He also made the carbides of the various metals, including the now common calcium carbide.  Among the problems that he undertook and solved was the manufacture of artificial diamonds.  He first made pure charcoal by burning sugar.  This was packed with iron in the hollow of a block of lime into which extended from opposite sides the carbon rods connected to the dynamo.  When the iron had melted and dissolved all the carbon it could, Moissan dumped it into water or better into melted lead or into a hole in a copper block, for this cooled it most rapidly.  After a crust was formed