CLAYS OF NEW YOKK ' 837 



often tlie predominating rock, tliongli from wea,tliering to an olive 

 color it does not always appear as distinctly ". 



" In the ravines in Chautauqua co., extending toward Lake 

 Erie, tlie shale still retains its green color ". 



Jamestown, Chautauqua co. This sample of shale came from 

 the bank of the Jamestown shale paving brick co. 



This was a rather gritty shale, which required 18.5^ of water to 

 make a workable paste ; plasticity, lean. The paste shrunk 4.5,':^ in 

 drying, and an additional 7.5^ in burning, making a total shrink- 

 age of 12^. Air-dried briquettes made of this mud had an average 

 tensile strength of 16 pounds a square inch, and a maximum of 20 

 pounds a square inch. This low tensile strength was due to the 

 silicious character of the shale which, however, permitted rapid 

 drying. 



Incipient fusion occurred at cone .04, vitrification at cone .01 

 and viscosity at cone 3. The clay burns to a deep red and dense 

 body. 



A sample collected by the writer a year later, representing an 

 average of the material used, gave: water required to mix up, 17^; 

 tensile strength, 45-69 pounds; plasticity, lean; incipient fusion 

 cone .06, with 5/^ shrinkage; vitrification .01, with 10^ shrinkage; 

 viscosity at cone 2. When vitrified the clay bums deep red. Sol- 

 uble salts .55^. 



Alfred center, Allegany co. Chemung shale is used at this 

 locality for the manufacture of roofing tile. The shale is some- 

 what argillaceous, and moderately fine-grained. 



It requires 20^ of water to make a workable mass, which is 

 slightly plastic. The shrinkage of this paste in drying is 4^ and 

 in burning 9^. The tensile strength of air-dried briquettes was, 

 on the average, 61 pounds a square inch, with a maximum of 62 

 pounds a square inch. 



Incipient fusion occurs at cone .06, vitrification at cone .01, and 

 viscosity at cone 3. 



