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Excerpt from Proceedings of the Academy of Natural Sciences of Philadelphia, 1882 Other pebbles of milky, smoky, and other quartz appear to have been derived from quartz veins of our neighboring gneiss rocks. Black pebbles found in the gravel used in the construction of the bed of the junction railroad just north of the city, and collected as specimens of basanite or touchstone, appear to be hornstone or chert, like that in the lower Silurian limestone at Easton. Numerous pebbles of the same kind are found on the Delaware shore at the latter place. Limestone itself appears to form no conspicuous element of our gravels. Though abundant in the same sources of supply of the common ingredients of the gravels, its fragments have been completely dissolved away Occasionally he had seen in the interior of a freshly broken pebble of black hornsto'ne, such as one presented this evening, minute rhombohedrons of calcite, while on the exterior minute cavities of the same form show where similar crystals have been dissolved. Pebbles of red sandstones and shales are frequent elements of our gravel, and have evidently been derived from the triassic rocks, so abundantly exhibited north of the city. Pebbles of compact quartz conglomerate are less frequent, and may probably have been derived from the same source. Or perhaps from the coal measures farther north. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

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