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some extent and employed for making pottery. Besides the 

 whiter varieties, there occur others of a dark blue colour, having 

 more or less sand and ferruginous matter in their composition. 

 Imbedded between the layers of clay are seams of white and 

 yellow sand. 



The clay beds of this locality would appear to occupy a middle 

 position in the formation, being higher than those southwest of 

 Woodbridge, but inferior to the strata of potters' clay near 

 South Amboy, to be next described. They lie very nearly in a 

 range with the white sandy clay seen near Albion Mill, with 

 •which also a dark blue argillaceous bed is associated. 



Potters' Clay, South Amhoy. — Somewhat higher in the order of 

 stratification, we find beds of bluish white and mottled clay, well 

 suited for the manufacture of a much esteemed variety of stone- 

 ware. 



This highly useful material occurs in a bed several feet thick, 

 ranging along the shore of the Raritan Bay fi'om South Amboy, 

 for a space of about two and a half miles, to the marshes called 

 the Cheesequakes. The stratum is nearly horizontal. Its upper 

 surface is washed by the tides upon the beach ; a mile farther to 

 the southeast, it rises twenty-five feet above the shore, and a few 

 hundred yards beyond this, it gently sinks again, so that two 

 miles from Amboy it is overlaid by the ordinary dark-blue as- 

 tringent clay. There are two principal banks or quarries where 

 this clay is procured on a rather extensive scale. In that nearest 

 to South Amboy, which goes under the name of Churchill's bank, 

 the mass has been excavated to the depth of twenty-five feet. 

 The lowest bed, which is that principally used, is a grayish blue 

 clay, which, on drying, becomes nearly white. Besides a large 

 proportion of alumina, it contains a large quantity of silica, in a 

 minutely subdivided condition. Scattered through it occur nume- 

 rous dark specks, which seem to be sulphuret of iron in a state of 

 decomposition. After the surface of this clay has been exposed 

 for some time to the air, these specks acquire a light yellow 

 colour, which most probably arises from the oxidation of the iron. 

 It is a curious fact, that the clay in which these dark specks are 

 seen, is preferred in the manufacture of the stoneware, for which 

 the material is chiefly used. Resting immediately above this 

 layer, there is a variegated or mottled variety, often most beau- 



