740 NEW YORK STATE MUSEUM 



tion at 1, witli 15^ shrinkage. Yiscosity at 5. Percentage of solu- 

 ble salts, .20^. 



About one mile nortb of the depot is the yard of the Garden 

 City brick company. This is on the site of the old Stewart yard, 

 but the plant is a modern one. The clay however is obtained 

 from the opening that supplied Stewart's yard. 



In the mining of the clay three kinds are recognized: 1) top 

 sandy clay; 2) middle clay and 3) black bottom clay. (For sec- 

 tion of bank, see chapter on " Geology of clay deposits in IsTew 

 York ", p. 605) 



ISTo analyses of the clay have been made, but no. 1 and a mix- 

 ture of 2 and 3 have been tested. JSTo. 1 is a red burning, gritty 

 clay, with an abundance of fine mica scales. With dl^ of water 

 it worked up to a very plastic mass, that had an air shrinkage of 

 5^. The tensile strength was low and ranged from 50 to 60 pounds 

 a square inch. The mechanical analysis gave 15. M sand, 83.75 

 clay substance and silt. In burning, incipient fusion occurred at 

 cone .03, with 11^ shrinkage; vitrification at cone 2, with 14^ 

 shrinkage, and viscosity at cone 5. Soluble salts, .54^. 



The mixture of 2 and 3 showed similar properties, but hardened 

 at a somewhat lower temperature. The tensile strength was from 

 40 to 50 pounds a square inch; the clay was slightly more gritty 

 than the top part, but was equally plastic; 33^^ of water was re- 

 quired to temper it; the air shrinkage was Qfo at cone .04 ; incipient 

 fusion occurred with a shrinkage of 12^; vitrification began at 1, 

 the shrinkage was 16^. The clay grew viscous at 5. The color of 

 the burned clay is light red, but deepens on hard firing. The solu- 

 ble salts amounted to .2^. 



The bricks made at these works are all dry pressed; the product 

 is used chiefly in Brooklyn. 



By mixing the clays, with addition of manganese, and by hard 

 or soft burning, the colors buff, pink, gray, brown, red, and speck- 

 led, are produced. 



