Report of Progress - 1883 Author:Unknown Author Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: and I am still in doubt where to place it if it exists. It seems to be younger than the Huronian." Gravels. The superficial covering of Chester county has bee... more »n derived from the immediately underlying rocks; for this part of Pennsylvania lies far south of the region of undisturbed Northern Drift, the southern boundary of which is marked by the great Terminal Moraine extending from the Delaware Water Gap to Olean on the upper Allegheny river, as described by Prof. H. C. Lewis in Report Z. On pages 327. '8, 337, however, gravel deposits are mentioned which are not referable to the mother rocks of the locality. One or two such were observed by Dr. Frazer in Lancaster county. Others of considerable size are shown by Mr. Hall on his map of Delaware county (Report C') and others on his map of the Philadelphia belt published in Report C8. These gravels lie at different heights aJbove tide level. The uppermost or Brynmawr gravel lies at about 400' A. T. The lower gravels are connected with the brick clay deposits ranging along the right slope of the Delaware river valley. The whole subject was assigned for special study three years ago to Prof. Lewis, who is preparing his report. The gravels of the State of Delaware come under the same general head, but differ among themselves as do those in Pennsylvania. An elaborate description of the gravel hills near Newark, by Prof. F. D. Chester, may be found in the American Journal of Science for January, 1883. The gravel there described is the Brynmawr gravel, covering island hills of decomposed gneiss. "The base of the two hills near Newark is not less than 80' above tide; one of the hills is 228' high, and a few of the largest bowlders rest at the summit; i. e., 308' A. T. The distance back from the river is 10 to 12 miles." ...« less