CLAYS OF NEW YORK 835 



-sandstones become more prominent, but to the west the shales in- 

 crease and predominate, so that along Lake Erie, " the Cashaqua 

 shale is succeeded bj a thick mass of black shale, and this again by 

 alternations of green and black shales ", which aggregate several 

 hundred feet in thickness. 



Angola, Erie co. The Portage shale is used by J. Lyth & Sons 

 at this locality for the manufacture of sewer pipe, fireproofing, 

 drain tile and terra cotta. The clay is somewhat less gTitty than 

 that at Jamestown. It is a grayish, moderately coarse-grained 

 shale and contains scattered streaks of bituminous matter. 



When ground to 30 mesh it required 21.4^ of water to work it 

 up, giving a moderately plastic mass. The air shrinkage was 4^ 

 and the fire shrinkage 10^. The air-dried briquets had an 

 average tensile strength of 92 pounds a square inch, and a maxi- 

 mum of 95 pounds a square inch. Incipient fusion occurs at 

 cone . 06, vitrification at cone . 01 and viscosity at cone 4. 

 The analysis of the clay is as follows •} 



Silica 65.15 



Alumina 15.29 



Ferric oxid 6.16 



Lime 3.50 



Magnesia 1.57 



Alkalis 5.71 



97.38 

 Total fluxing impurities 16 . 94 



In general composition it resembles a Carboniferous shale used 

 for paving brick at Kansas City, Mo.^ This shows the following 

 analysis: 



Silica 64.37 



Alumina 19 . 73 



^ Bulletin New York state museum, no. 13, v. 8, p. 228. 

 ^ Clay worker, December 1893. 



