J. H. McF.—A fine quality of kaolin.—F. C. H.—The floury powder consists chiefly, if not altogether, of calcium carbonate.—C. L. G.—They are all silicious limestones. We cannot judge fairly of their value for building purposes from the powders sent.—D. K.—Ferruginous earth or marl.—A. E.—It is a partially decomposed feldspar. The white powder is for the most part an impure, silicious, kaolin.—E. H.—It consists chiefly of basic carbonate and hydrated oxide of lead—poisonous.—J. B. V.—It is a fair quality of pipe clay—impure silicate of alumina—probably worth about $2 per ton in New York.
COMMUNICATIONS RECEIVED.
The Editor of the Scientific American acknowledges with much pleasure the receipt of original papers and contributions on the following subjects:
Religion. By W. M. E.
Cause of Explosion in Flouring Mills. By G. M.
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