832 • NEW lOKK STATE MUSEUM 



Along tlie banks of Seneca and Cayuga lakes the full section of 

 the Hamilton gioup may be seen. The lower members are the 

 most northern, and dip to the south under the higher ones. Prof. 

 Hall makes the following divisions: 



1 Dark, slaty fossiliferous shale, resting on the Marcellus shale 



2 A compact, calcareous blue shale, of little thickness 



3 An olive or blue shale, which in its upper layers is stained by 

 oxid of manganese. This is one of the best adapted for clay 

 products 



4 Ludlowville shales, often sandy in their nature 

 6 A limestone 



6 Moscow shales, of grayish blue color, and slightly calcareous in 

 places 



These subdivisions can all be seen along the eastern shore of 

 Cayuga lake from Springport to Ludlowville. 



Cairo, Green co. This is one of two localities at which the Ham- 

 ilton shale is mined. The material, which is shipped to the works of 

 the Catskill shale paving brick co., at Catskill, is a reddish gritty 

 shale possessing little plasticity. This material was at first used 

 alone, but found difficult to work on account of its excessive lean- 

 ness, and consequently is now mixed with bOfo of common red clay 

 also obtained from Cairo. Samples of this mixture were tested with 

 the following results. The moderately plastic paste shrunk 4)^ 

 in drying, and 9^ in burning. Air-dried briquettes had an average 

 tensile strength of 9Y pounds a square inch, and a maximum of 100 

 pounds a square inch. 



Incipient fusion occurred at cone .05, vitrification at cone .01, 

 and viscosity at cone 2. 



The mixture of clay and shale is ground in dry pans, then passes 

 to the pug mill on the floor above, whence, after tempering, it is 

 discharged to the auger side-cut machine. The bricks are re- 

 pressed, dried in tunnels, and burned in down-draft kilns. The 

 company has recently erected a large continuous kiln; in this kiln, 

 most of the firing is done in temporary fireplaces built in the door- 



