T60 NEW YOKK STATE MUSEUM 



one of those used by the iNTew York architectural terra cotta co. 

 It possesses the advantages of being very plastic, burning to a 

 deep red, with a very dense body at a comparatively low tempera- 

 ture. It took 33. YO^ of water to work it up. The air shrinkage 

 was 6^, and at .06, 9.5/^. Incipient vitrification began at .03, 

 with 12^ shrinkage; complete vitrification was reached at 4. 

 Viscosity at 6. The percentage of soluble salts contained in the 

 clay was .25^. The tensile strength showed a minimum of 75 

 pounds and a maximum of 90 to the square inch. The clay slakes 

 quite rapidly in water. 

 Its composition is 



Silica 67. 00. 



Alumina 29.20 



Ferric oxid 4.80 



Lime ,. ., ,. . . . .65 



Magnesia .31 



Alkalis 1.80 



Water ,. 6 . 10 



Total .... 



Olens Falls. Two varieties of clay occur here in the pits of the 

 Glens Falls terra cotta co., the upper being red, and the lower 

 bluish gray. The composition is indicated by the following 

 analyses. 



^'"'^^ Red. 



gray 



Silica 48.35 57.46 



Alumina . .' 11.33 21.15 



Oxid of iron 4. 02 5 . 52 



Lime ..15.38 3.65 



Magnesia 3 . 17 1.50 



Organic matter 1 . 18 .... 



Alkalis 6.05 4.72 



89.48 94.00 



