Berlin collection appear quite black by reflected, though translucent by transmitted light, and that this black substance lying in the little irregularities of the surface is found by its behavior in fused nitre to be graphite. The relative ease with which graphite and diamond burn was determined by exposing them to the same temperature for the same time, when the following amounts of the three specimens were consumed: Foliated graphite 27.45 per cent. Diamond 97.76 „ „ Granular massive graphite 100.00 „ „ “In a superb cut diamond weighing between six and seven carats, the brilliancy of the stone was decidedly increased after the operation. The loss of brilliancy observed by Mr. Schrötter is a proof, in M. Baumhauer’s opinion, that notwithstanding the precautions employed, the diamond had come in contact with the oxygen of the air, or else that at so elevated a temperature a reducing action had been effected upon the magnesia (in which the diamond had been packed) by the diamond, which had then been superficially burnt by the oxygen of that earth. A diamond which presented to the naked eye an appearance of dirty green was treated in a similar manner; examination with a lens showed that the color did not extend to the entire stone, but was confined to small portions, which formed small green clouds in the centre of the mass. After heating to a white heat in hydrogen, the brilliancy of the surface remained as before; the transparency was rather increased than diminished, but the green hue was transformed into pale yellow. Another small diamond, of so dark a green as to approach black, and almost opaque, assumed a violet hue, retaining, however, its brilliancy, and becoming more translucid. A small cubic diamond of light green color preserved its brilliancy and transparency intact, but lost its color completely. No difference in its weight before and after the operation could be perceived.