1896.1 MICROSCOPICAL JOURNAL. 209 



acters of the coveted diamond; and even at tlie present 

 time we are apprised that ^I. Henri Moissan of Paris, 

 has produced by the electrolytic union of boracic acid 

 and carbon, a mineral substance, which proves to be the 

 hardest known substance in nature, as it readily wears 

 away the diamond lieretofore known as at the head 

 of the list of minerals in hardness, and that the 

 new mineral substance may be produced in commercial 

 quantities; but as it is likely to remain for a considerable 

 period or lapse of time a mineral curiosity, not readily 

 accessible to the working w^orld, we can at least congratu- 

 late M. Moissan on his success in its production as a min- 

 eralogical novelty. Previous to the announcement of M. 

 Moissan's various electrolytical furnace ^jroducts, a new 

 abrasive substance had already been heralded, far and 

 wide, as the discovery of an American citizen. This sub- 

 stance became known under the trade name of carborun- 

 dum, aiid was promptly introduced among the trades 

 heretofore using emery and corundum as being in some 

 cases superior in its cutting or abrading qualities. This 

 material proved to be a result of an electrolytical union 

 of Silex, Alumina and Carbon; and presenting itself in 

 the shape of very small crystals of a distinct crystallo- 

 graphic system, of bluish and greenish hues. The dis- 

 coverer of this new substance protected his process by a 

 patent, and thus put it on a commercial basis. After the 

 new substance had been announced as a candidate for 

 public favor, I became very much interested in it, and 

 finally became aware of its character and properties, as 

 adapted to dental tools, and of its remarkable efficiency 

 in cuttino; awav the enamel of teeth. For several years 

 previous to the announcement of the production of Car- 

 borundun, I had at intervals studied the products re- 

 sulting from the electric combustion of carbon rods, in 

 the hope of detecting some interesting microscopic char- 



