I. C. Russell — Glacial Records in the Newark System. 499 



size of a pin- head to microscopical dimensions. They were 

 evidently not composed of hornblende, and I hesitated to pro- 

 nounce them greensand, which material Mr. Pourtales, in 1869, 

 reported to exist in the sands oft* Long Branch and Rockaway 

 Beach.* Mr. McGee was kind enough to have an examination 

 made in the laboratory of the IT. S. Geological Survey and 

 informs me "that the black grains are, as Count Pourtales 

 supposed, glauconite. The mineral seems to have undergone 

 a curious alteration and the grains were polished through attri- 

 tion and partly through chemic and mechanical alteration akin 

 to that of nodulation, but the density, optical properties, hard- 

 ness, etc., of the broken grains are identical with the like prop- 

 erties of New Jersey greensand from the Cretaceous and 

 Eocene." It was an open question with Mr. Pourtales whether 

 these grains were washed out to sea from the marl beds of 

 New Jersey or belonged to beds cropping out at the sea bottom. 

 In view of the great extent of ground over which these grains 

 are spread, and the great distance from the New Jersey coast, 

 close to Montauk Point for instance, the first supposition can 

 no longer be maintained ; they must be treated either as be- 

 longing to marl beds laid bare by the sea or as the remnants 

 of such which have been destroyed by the sea. I Whether 

 these beds were Cretaceous or Eocene strata is a question 

 which probably can only be decided upon paleontological 

 grounds, but the preponderant strength of the Cretaceous on 

 the mainland certainly speaks in favor of the latter having sup- 

 plied the greatest amount of greensand grains to the ocean's 

 bottom. 



March 26, 1891. 



Art. LX. — Are there Glacial Records in the Newark Sys- 

 tem? by Israel C. Russell. 



Several expressions of opinion have been published by 

 geologists in this country, respecting the existence of glaciers 

 along the Atlantic border during the deposition of the rocks of 

 the Newark system. It has been recently stated by Prof. J. D. 

 Dana,J that this period u ended in a semi-glacial era, as is 



* Appendix, No. 11, TJ. S. Coast Survey, Report of 1869, also Petermann's 

 Geogr. Mittheilungen, vol. xvi, pp. 393-398. 



f Quartz sand. and pebbles, and greensand (perhaps hornblende) seem to be 

 the only minerals which preserve their integrity in moderate depths at the bottom 

 of the ocean; feldspar and mica are rarely found, and the so-called "mud" 

 consists very often of the finest sand with some mica flakes, and with a just 

 sufficient admixture of clay to produce cohesion. 



% This Journal, III, xl, 1890, p. 436. 



