LVIII. On the Chemistry of some Carboniferous and Old Red Sandstones

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Sandstone is generally understood to consist of quartz grains—popularly called sand—bound or cemented together into a more or less compact mass, the cementing material consisting of such substances as the carbonates of iron, lime or magnesia, clay, and silica. It is not my intention at present to enter into the origin of sand, but rather to draw attention to the nature of the cementing and colouring materials of some sandstones of the Carboniferous and Old Red formations, and more particularly those found in the neighbourhood of Glasgow. On the Nature of the Cementing Material. —Sandstone may have been cemented together by the decomposition or re-arrangement of some of the constituents previously in the sand, or by the addition of such substances as carbonate of lime, and oxide of iron, deposited from springs. Professor Church, in some interesting notes on the recent formation of some rocks, observes, “that at Bude Haven, Cornwall, and elsewhere, coarse grained sand is in many cases being cemented together by the action of the water of land springs containing carbonic acid, which, percolating through the sand and dissolving the fragments of shells contained therein, the carbonate of lime is subsequently at some other point slowly deposited as the carbonic acid escapes, thus forming a cementing material for the sand.” In cases where the quantity of carbonate of lime is large, it may probably have been derived from adjacent limestone rocks. When we place a few fragments of a sandstone in hydrochloric acid and apply heat, we are This 250-word extract was created in the absence of an abstract