696 



Report of the State Geologist. 



olive or green. The shales sometimes pass into shaly sandstones, and these 

 are often highly micaceous. The members of the group recognized by Pro- 

 fessor Hall, beginning at the top, are : 



6. Sandstone and conglomerate. 



5. Old red sandstone. 



4. Grey and olive shales and shaly sandstone. 



3. Green shale with grey sandstones. 



2. Black, slaty shale. 



1. Olive, shaly sandstone. 

 Portage sandstone. 



Of these members 2, 3 and 4 are the most important to clay workers, and 

 the beds of shale exposed are often twenty or thirty feet in thickness and free 

 from sandstone. 



•" On the Genesee river the shale is often in thick beds of a bright green 

 color and scarcely interrupted by sandy layers." 



" AVestward from the Genesee river there appears to be a constant aug- 

 mentation in the quantity of the green shale, which is often the predominating 

 rock, though from weathering to an olive color it does not always appear as 

 distinctly." 



" In the ravines in Chautauqua county, extending toward lake Erie, the 

 shale still retains its green color." 



Jamestown, Chautauqua county. This sample of shale came from the 

 bank of the Jamestown Shale Paving Brick Company. 



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

 make a workable paste ; plasticity, lean. The paste shrunk 4.5 per cent, in 

 drying, and an additional 7.5 per cent, in burning, making a total shrinkage 

 of twelve per cent. Air-dried briquettes made of this mud had an average 

 tensile strength of sixteen pounds per square inch, and a maximum of twenty 

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

 character of the shale which, however, permitted rapid drying. 



Incipient fusion occurred at 1,950° F., vitrification at 2,050° F., and 

 viscosity at 2,200° F. The clay burns to a deep red and dense body. 



Alfred Centre, Alleghany county. Chemung shale is used at this locality 

 for the manufacture of roofing-tile. The shale is somewhat argillaceous, and 

 moderately finegrained. 



It requires twenty-two per cent, of water to make a workable paste 

 which is slightly plastic. The shrinkage of this paste in drying is four per 



