CLAYS OF KEW YORK 739 



sectional roofs whicli are hinged and can bo lifted by a lever for the 

 purpose of admitting more sunlight. The bricks are burnt mth 

 wood in clamps; the product is shipped to various points on Long 

 Island. 



Below is given an analysis of the lower clay. 



Silica 62.39 



Alumina 23.60 



Oxid of iron 3 . 39 



Lime 70 



Magnesia 10 



Alkalis 5.89 



96.07 



The physical properties of the two clays from Meyers' s bank are 

 as follows: 



Upper clay. While this differs from the lower clay in color, 

 because of the higher oxidation of the iron oxid, at the same time it 

 is more sandy, containing a large amount of very fine sand and 

 mica scales. It is quite plastic and tough, but not very tenacious, 

 as shown by its low tensile strength, which ranges from 20 to 25 

 pounds a square inch. It took 34.70/^ of water to work it up; the 

 bricklets showed an air shrinkage of ^ic At cone .08 the clay bums 

 bright, but not dark red, with a total shrinkage of 7^. Incipient 

 fusion occurred at cone .05 with a total shrinlvage of 10/^. The clay 

 had a shrinkage of 14^ when vitrification began at cone 1. It be- 

 came viscous at cone 4. The soluble salts amounted to .14/^^. 



Bottom clay. This is more plastic and slightly more tenacious 

 than the top clay, but otherwise does not differ from it very much. 

 It absorbed 28^ of Avater in tempering — the air-dried bri- 

 quettes had a tensile strength ranging from 30 to 40 pounds a square 

 inch. The air shrinkage was 8^. At cone .08 it amounted to 8^/^, 

 at cone .05 to 10/^. Incipient fusion occurred at cone .04, vitrifica- 



