G84 KEW YOKK STATE MUSEUM 



Stratum 3 was rejected because quite deficient in clay and 

 silica. 



Stratum 4 was characterized as a poor rock, which might be 

 used if necessary, but was not recommended, being deficient in 

 clay. 



Stratum 5 was marked as being a slight improvement over 4, 

 owing to the smaller amount of carbonates it contained, though 

 deficient in clay. 



Stratum 6 was too rich in carbonates and too low in alumina, 

 or clay, to be used for hydraulic cement. 



Stratum 7 was the most silicious of the series, though it con- 

 tained little clay. With care in burning it could be used, as the 

 silica present was in a fine state of division. It is, however, not 

 an entirely satisfactory rock. 



Stratum 8 proved a good stone for this quarry. 



Stratum 9, in both its light aiid. dark forms, was,, besides hav- 

 ing great :lack of uniformity, too rich in carbonates and deficient 

 in insoluble matter. By itself this stratum would prove ^ poor 

 one. 



Stratum 10 was excellent and recommended for use. 



Stratum 11 appeared at a glance to be insufiiciently hydrau-!c 

 and was excluded. . . 



Of all these strata, for one or more reasons, only those num- 

 bered, 5, 8, and 10, were considered fairly good rock if burned 

 by themselves. It was possible, however, to mix different strata 

 and thereby obtain a mixture of the proper quality. 'No. 7 was 

 consequently included, and the cement so prepared analyzed as 

 follows: 



Loss on ignition 8.29 



Uncombined silica 16.3 



Combined silica 13.5 



Alumina and iron oxid 11 . 04 



Lime 33 . 36 



Magnesia 15. 5S 



Sulfuric acid .4 



Alkalis 1.5 



