CLAYS OF NEW YOKK 591 



At Coeymans Landing the terrace is 140 feet, and it rises to 177 

 feet at the West Shore railroad station, about a mile from the river 

 then a hill hides the farther continuation of it from view. Between 

 South Bethlehem and Callanans Corners the shore line of the 

 terrace along the base of the Helderberg escarpment is well seen. 



From Catskill up to Albany the terrace at most points is very- 

 wide. At Coxsackie it extends behind the hill to the south of 

 the town and comes down along Murder creek to Athens. From 

 Albany an alluvial plain, belonging to this formation, spreads 

 westward, reaching a hight of 360 feet near Schenectady. The 

 surface of these terraces is usually a loamy soil of much agricul- 

 tural value. 



Following up Croton river as far as Croton lake, remnants of 

 terraces are seen at various points, their hight above the river bed 

 decreasing as we recede from the Hudson. The majority of these 

 detached pieces seem to belong to a terrace formed at the same 

 time as the 100 feet one at Croton landing. There are at a few 

 places traces of a second and lower terrace, and beside this a 

 third one, which is being formed by the river during its floods at 

 the present day. 



From the facts as observed, quoted above, the following may be 

 deduced. That during the retreat of the ice sheet from the Hud- 

 son valley the glacial streams deposited as kames a great amount 

 of ground up material, principally shale, the material found under- 

 lying the clays along the upper portions of the valley. 



That subsequent to the retreat of the glacier there was a depres- 

 sion of the land, which, according to Dr Merrill,^ amounted to 80 

 feet at ISTew York city and near Schenectady to about 360 feet. 



During this period a great amount of plastic clay was depos- 

 ited, produced by glacial attrition of the shales and limestones, 

 the latter no doubt giving to it the marly character and influencing 

 its color. 



The upper portion of the clay is more silicious, and overlying it 

 is an extensive deposit of sand, indicating a change in the nature 



1 Amer. jour. set. June 1891. 



