GLACIAL GEOLOGY OF THE SCHENECTADY QUADRANGLE 25 



dry seasons of the year when the surface soil has been largely de- 

 prived of water by evaporation, an upward movement of the ground 

 water by capillarity takes place. If the ascending ground 

 water carries iron in solution the iron may be oxidized and pre- 

 cipitated as it approaches the surface. In this way the film of iron 

 oxid coating the particles of sand is formed. The porosity of sand, 

 admitting air to a considerable depth below the surface and at the 

 same time favoring evaporation, facilitates the process. In addition 

 to the iron it is probable that small particles of clay are carried up- 

 ward by the moving ground waters and are fixed through cementa- 

 tion by the iron oxid. These processes continue from season to 

 season through a long period of years, the layers of molding sand 

 being periodically added to at the bottom until it attains such a 

 thickness that surface influences no longer penetrate it. 



Sands for making sand-lime bricks. The Lake Albany deposits 

 furnish sands which are adapted for use in the manufacture 

 of sand-lime bricks. This industry has recently been estab- 

 lished in the vicinity of Schenectady. There are two plants 

 for making the bricks on the line of the Delaware & Hudson 

 railroad between Schenectady and South Schenectady. At one of 

 the plants the sand selected for this purpose was a somewhat 

 coarse, sharp-grained sand of gray color. It was evidently a water- 

 sorted sand, as it was evenly stratified and occurred in a pocket, sur- 

 rounded by sands of different color and texture. At the other plant 

 the sand used was less distinctive, being of the color and texture 

 common to the mass of sands in that locality. At this plant the sand 

 was first sifted to remove gravel. 



Sand for making cement blocks. This industry has recently 

 been developed to a considerable extent in the vicinity of Schenec- 

 tady. There are a large number of small plants and as the ap- 

 paratus used is simple it is readily moved from place to place. The 

 sands selected for this purpose are the sharp or angular grained 

 sands that occur in pockets as above described. 



Brick clays. Though probably belonging to a later geological 

 stage than the Lake Albany deposits described above, mention may 

 here be made of a deposit of Pleistocene clays which is used for 

 making red brick. The bed is located about half a mile from the 

 highway bridge which crosses the Mohawk below Schenectady and 

 near the Delaware & Hudson railroad tracks. The clays are yel- 

 lowish and bluish in color, the colors showing in the layered arrange- 

 ment of the materials. They are of firm, compact texture. The 



