CLAYS OF NEW YOEK 833 



ways of the kiln, no grate bars being used; it is said that prac- 

 tically no fuel is charged through the small openings in the roof 

 of the kiln. 



The Hamilton shale is also utilized in the western part of the state 

 at Jewettville, where dry pressed and also stiff mud brick are made 

 from it. (See detailed account of brickyards, p. 724) 



Several samples have been collected by Prof. I. P. Bishop in 

 Erie co., and tested with" the following results. The numbers pre- 

 ceding each locality refer to Prof. Bishop's notes. 



1^0. 2. Hamilton shale from near Windom. Forms a bed 

 10-12 feet thick. When ground to 30 mesh, it took 22^ of water 

 to work it up. The mass was fairly plastic. The tensile strength 

 was 40 pounds a square inch, and the air shrinkage 4-|/^. 



At .03 the total shrinkage was 9fo. The brick was deep red, hard 

 and semi-vitrified. Vitrification occurs at cone 1, with a total 

 shrinkage of 14;^ and viscosity at 4. The shale is slightly calca- 

 reous, and the soluble salts were noticeable on the surface of the 

 dried bricklet. A determination of these showed 9^. 



'No. 3 of Bishop is a 5 foot bed above the preceding one, and 

 took only 20^ of water to work it up. The air shrinkage was 2^. 

 At .06 the total shrinkage was 4^; the color of the bricklet deep red 

 when incipient fusion had been reached. It vitrified at 1 with 8^ 

 shrinkage. Viscosity began at 4. The percentage of soluble salts 

 was Qfe. The analysis yielded: 



■Silica 57 . 30 



Alumina 21 . 61 



Perric oxid 6.50 



Lime 2.52 



Magnesia 1.50 



Alkalis 



Water 7.80 



No. 4 of Bishop is from the top of the Hamilton shale at bridge 

 west of Websters Cbmers. The bed is 5 to 6 feet thick. Tliis 



