experiment continued tbr more than two mouths; the negative pole was covered with a black layer.
" Nothing was discovered in this layer by an examination with a microscope.
" I requested M. Gaudin, known to the Academy by dif[~rent researches, to try both products on hard stones.
" He proved, in my presence, that the small quantity of" material that surrounded one of the dozen wires of platinum, mixed with a little oil, sufficed to polish in a short time several rubies.
" The black powder deposited in the humid way, although much more considerable in quantity, required more time to produce the same polish.
"We know that the diamond is the only body which polishes the ~ ruby ; therefore M. Gaudin has not hesitated to consider both materials as the powder of the diamond.
"I have made a great many experiments during two years ; I give. here the two which afford the most interesting results."
In connection with the above we note a communication to the French Academy of Sciences,* from M. Lionnet, in which he claims to have made, in 1846 and 1847, experiments on the crystallization of cnrbon. These experiments, since forgotten, were recalled by a communication of Chancourtois t to the Academy. M. Lionnet claims to have used the following process : A voltaic couple, ibrmed of platinum and tin, was plunged in a small vessel filled with carbon bisulphid% under the action of the weak current so developed~ decomposition of the electrolyte occurred, the sulphur combining with the tin, while tim carbon, the author claims, was deposited in a crystalline condition on the bottom of the vessel. It would seem that if deposited at all under these conditions, it would be on the surface of the I)latimnn.
Central High School, Philadelphia, Aug., 1880.
Lunar Geology. J. Landerer has submitted to tile Academy a work in which he seeks, ~ to determine tile lithologic eharaeter of our s ttellite. He thinks that tile density of tile moon, and the angle under which it polarizes the light of tile sun, are such as to show that tile materials of the surf~tce are analogous to th~se of the silicate rocks.-