CLAYS OF NEW YORK 595 



yellowish brown sand, yellowish brown clay and stiff blue clay, 

 the latter being rather calcareous. The upper clay is somewhat 

 silicious, and its coloring is due to the weathering of the lower 

 layer. This formation has a thickness of about 15 feet, but some- 

 times, as at Burlington, it reaches a thickness of 100 feet. Iso- 

 lated boulders are occasionally found in the clays, and are con- 

 sidered by Emmons to have been dropped there by icebergs. The 

 clays are usually horizontally str>atified, and contortions of the 

 layers are extremely rare. ISTumerous fossils have been found in 

 the overlying sands, among them being Saxicava rugosa 

 Lamarck and Tellina groenlandica Beck, which are 

 very common; Tritonium anglicum, Tritonium 

 fornicatum, Mytilus edulis Linn., Pec ten islan- 

 d i c u s Chemnitz, Mya truncata Linn., M. arenaria 

 Linn., IN'ucula portlandica; the skeleton of a whale has 

 also been found in these deposits.-^ 



Openings have been made in them for the purpose of obtaining 

 brick clays at Plattsburg and a few other localities, but, owing to 

 the lateness of the season when I visited them, information was 

 hard to obtain. 



Long Island clays 



Long Island is made up of a series of sands, gravels and clays, 

 which form two parallel ranges of hills in the northern half of 

 the island, while the southern half is a flat plain. The most 

 southern of the ranges represents the limit of the drift.^ 



The clay beds are exposed along the north shore of the island 

 and at several points along the main line of the Long Island rail- 

 road. In describing them I have gone east along the north sliore 

 and come back through the center of the island. 



In a paper on the geology of Long Island, (previously cited) 



1 The writer has found one species of diatom belonging to the genus diatoma, 

 in the clay from Plattsburg. 



2 For a detailed account of the topography of Long Island see Mather, 

 Geol. Neio York, 1st dist. 1S43; W. Upham, A. J. S., Ill, 18; F. J. H. Mer- 

 rill, " Geology of Long Island," Ann. N. Y. acad. scl. 1884. 



