On the included Rock-fragments of the Cambridge Upper Greensand

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Abstract
From time to time fragments of various rocks have been noticed in the formation of such size and angularity as to have suggested the idea to two preceding observers (Mr. Bonney and Mr. Seeley) that they might have been brought to their present position by the agency of ice. While ignorant of the suggestions of these gentlemen, we were forced independently to the same conclusion, and commenced, together, an examination of the subject. Our first step was to make an examination of all the erratics from the formation which had been preserved in the various local collections. The following is a descriptive list of the most important of these fragments. Descriptive List of Rock-fragments . No. 1. A large cuboidal block of coarse yellowish felspathic grit, very hard and compact, measuring 10 x 7 x 7 inches, subangular, not much decomposed; incrusted with coprolite, Exogyra, Spondylus truncatulus, Plicatula sigillum , and Ostrea vesiculosa . Derived probably from the Millstone-grit of the north of England. Collection , Woodwardian Museum, signified after this by the initials W. M. No. 2. A very angular, roughly rhombohedral prism of purplishred indurated shale, moderately hard, measuring 9 x 5 x 5, not much water-worn or decomposed; incrusted with coprolite and P. sigillum . Derived probably from Old Red Sandstone of Scotland. Collection W. M.; in Mr. Browne's collection is a smaller piece. No. 3. A larg subangular block of soft friable grey sandstone, measuring 14 x 12 x 6 inches; rather rounded and water-worn; intrusted with coprolite and P. sigillum .

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