GEOLOGIC FORMATIONS OF NEW YOEK 177 



tance and dropped to form the flood plains and terraces which 

 border our river valleys and the hills of sand and gravel in the 

 valleys which are called kames and eskers. Where there were 

 bodies of still water the finer materials were dropped to form 

 clay. \ ' 



At this time the country was deeply submerged and tide water 

 filled the valley of the Hudson river and Lake Champlain so 

 that the Gulf of St Lawrence and New York harbor were united. 

 This is evidenced by the fact that near the St Lawrence and 

 Lake Champlain, above the gravel beds, are some beds of clay 200 

 feet thick or more, which contain marine shells of species now 

 existing on the coasts of New England and Canada. These show 

 that, since such shells were living, those valleys have been de- 

 pressed below the sea-level, long enough for these deposits of clay 

 to be formed. They are known as pleistocene clays. The Hud- 

 son river valley clays are their southern extension, but contain no 

 fossils. i.:--" :.-v m 



The Quaternary deposits of New York are, therefore, chiefly 

 those made in the presence of the ice and those resulting from 

 the working over of the glacial deposits by running water. In 

 this latter process the angularity of the glacial boulders and 

 pebbles has been worn off. The evidences of glacial action are 

 well seen in almost all parts of this state. Almost every gravel- 

 bank consists of waterworn fragments of the old rocky strata; 

 pebbles of limestone, sandstone and slate, with some of gneiss 

 and granite, which universally appear to have been transported 

 from north to south. From a bushel of pebbles taken from any 

 gravel bank south of the Erie canal, the geologist can pick out 

 specimens of almost every stratum which is exposed north of the 

 bed whence they were taken. South of the line of outcrop of 

 the Helderberg limestones, the gravels are full of fragments of 

 their different layers; and among them lie worn pieces of the 

 red Medina sandstone, others of the Hudson river group, and 

 others of still more northern strata ; while some are granite peb- 

 bles, which must in many instances have come from Canada. 

 They have evidently been transported from north to south in 



