ISO 



the series are preserved; and hence we have in that locality the 

 white clays and sands of the " clay banks." 



This lowest division of the upper secondary series passes into 

 the greensand formation by a gradual transition ; we cannot, 

 therefore, delineate very precisely, the limit which separates the 

 areas of the two formations. It will be traced with as much 

 minuteness as practicable when we give the ascertained boundaries 

 of the greensand or marl tract, being the northu'estern margin of 

 that important belt. It will be sufficient for our present object to 

 state that this line, bounding these inferior clays and sands on the 

 southeast, ranges nearly parallel with the railroad which unites 

 South Amboy with Bordentovvn, lying southeast of it at an 

 average distance of about three miles. Between Bordentown- 

 and Salem it preserves a rather greater distance from the Dela- 

 ware. 



Besides the tract thus traced, embracing most of the deposits 

 of pure potters' clay in the State, there occurs an isolated bed of 

 remarkably pure white clay and sand, which obviously belongs 

 to this formation: it lies between Woodbridge and the Raritan, 

 having escaped the destructive diluvial action which has swept 

 away so large a portion of these lower beds of the formation in 

 other places. 



Composition. — White and yellowish sands, and white-blue and 

 mottled-blue, and pink clays, used in pottery, occur abundantly in 

 the lower and middle portions of this formation. Higher in the 

 series these beds become less predominant, and we meet with a 

 larger proportion as we ascend, of darker, more ferruginous and 

 carbonaceous sands and clays. A very common material among 

 these is a dark, sandy, micaceous clay. This deposit when moist, 

 is usually lead-coloured or a dark-blue, or sometimes almost 

 black. In this state it is somewhat plastic, becoming as it dries, 

 of a light bluish-gray colour. It is rarely free from a consider- 

 able proportion of ordinary siliceous sand and mica, both usually 

 in a state of minute division. The dark colour seems chiefly to 

 arise from a small quantity of carbonaceous matter in a diffused 

 condition. Relics of vegetation, such as carbonized wood or 

 lignite, amber, and retinasphaltuin, often occur in it, but par- 

 ticularly the first. It exhales the smell of marsh mud, though 

 this gives place occasionally to that of sulphur, emitted by 



