I08 NEW YORK STATE MUSEUM 



These beds form only a part, but are perhaps as important as any, 

 of the valued clays of the Hudson valley. 



These deposits are very similar in appearance. The lower por- 

 tions are usually bluish and the upper yellowish in color. The 

 laminated character is best shown in the upper layers. Thin laminae 

 of sand occasionally appear, in some places forming such proportion 

 of the masses as to require no admixtures of that material in the 

 process of brick manufacture. The coarser sandy material over- 

 lying the clay, when screened, furnishes sufficient quantities of sand 

 when that is required, which is usually the case on account of the 

 purity of the clay. 



The chemical composition of the clay at Roseton is given from 

 the following analysis :^ 

 SiO, 55.00 



AiAl 34 



Cab 5 



MgO. , 3 



K.O I 



NaO( 



Combined H^O 

 Moisture i 



22 



100.00 



Both the blue and yellow clays are calcareous and effervesce 

 with acid. They have been used as marls on account of their lime 

 content. The yellow color is due to oxidation. The clays are used 

 entirely for brick. 



Clay deposits also occur at Arlington, a mile east of Poughkeepsie, 

 and are used for brick. The clay which is fairly abundant along 

 the banks of Casper creek in the neighborhood of Arlington is 

 covered with some sod, but is easily exposed by stripping this off. 

 Yellow clay is underlain by blue clay. 



It seems possible that the deposits at Arlington were accumulated 

 in lacustrine waters, perhaps impounded by stagnant ice at the 

 mouth of Casper creek. The kames (see plate 21) that now lie 

 near the mouth of the creek may have been left by the melting of 

 such a mass of ice. 



Limestone quarries. Quarries have been opened at places in 

 the limestone strips of the Wappinger creek belt. The largest of 

 these is Stoneco quarry, operated by the Clinton Point Stone Com- 



1 Ries, N. Y. State Mus. Bui. 35, 1906, p. 381. 



