26 NEW YORK STATE MUSEUM 



bed is overlaid by a thickness of one or two feet of sand or sandy 

 clay which is mixed with the stiff clays in proportions proper for the 

 purpse of making bricks. The areal extent of this deposit of clays 

 is said to be about 25 acres. 



LAKE ALPLAUS DEPOSITS 



The region of country traversed by Alplaus kill presents striking 

 topographic features. At High Mills the creek enters a rocky gorge 

 from which, after a descent of 40 feet in the course of a mile, it 

 emerges on the floor of the Ballston channel. West of High Mills 

 on either side of the creek are deposits of morainic character con- 

 tinuous with the morainic hills of the Burnt Hills district, already 

 described. Farther to the west the creek lies in a broad valley 

 bounded on either side by an extensive, nearly level area having an 

 elevation of 420 feet. The materials of this area are stratified clays 

 and sands of evident lacustrine origin. To the body of glacial 

 waters in which these deposits were laid down I have given the name 

 of Alplaus lake. 



A section of the deposits is shown where the road crosses a branch 

 of the Alplaus kill about one mile west of High Mills as follows : At 

 the base about 10 feet of blue boulder clay with gravel; then 4 feet 

 of dark evenly stratified clays overlaid by about 2 feet of yejlowish 

 clays, evenly stratified ; then, at the top, 3 feet of sand and gravel. 

 The sand continues as the surface soil in the adjoining fields attain- 

 ing a level 10 feet higher than the top of the section. Farther to the 

 west the deposits are of somewhat coarser materials. In many 

 places fine gravels occur, as along the road that runs northerly to 

 Charlton village. 



The conditions under which Lake Alplaus was formed and the 

 subsequent events resulting in the present topography are clearly de- 

 ducible from the above data. 



With the melting of the ice sheet a mass of debris was heaped 

 up in the Burnt Hills district, forming morainic hills with an eleva- 

 tion of upwards of 420 feet. 



The belt of morainic materials lay across the floor of the deepest 

 portion of the Glenville rock basin in the locality west of High 

 Mills. 



Glacial waters became ponded back of the moraine dam, forming 

 a lake. In this lake sediments were deposited ; at first from streams 

 derived from the melting ice and later from Alplaus creek, draining 



