CLAYS OF CRETACEOUS FORMATION. 191 



horizon. Locally there are several such layers separated by thin 

 beds of sand. In the latter case they might very well be classed 

 with the laminated clays and sands. The best of these black clay 

 beds were formerly much used for pipe, and are now in demand 

 for conduits, speckled brick, front brick, etc. At Cutter's and 

 Pratt's banks a thin bed (2 to 3 feet) of buff-colored clay, — known 

 as rockingham clay — occupies about the same relative position 

 respecting the fire clay as did the "top-white" clay in the banks 

 near Keasbey. 



\\ "here best developed these various beds — the sandy leaf-bear- 

 ing clay, the top-white, pipe and rockingham clays — do> not ex- 

 ceed 15 feet in thickness. They are nowhere so sharply marked 

 in their contacts and so distinctive in their characteristics that 

 they can not be regarded as parts of the laminated clays and sands, 

 which form the upper half of the Woodbridge clay. The varying 

 orders of stratification of the Woodbridge clays is shown by sev- 

 eral detailed sections which are given in Chapter XIX, in con- 

 nection with the discussion of the clays from Middlesex county. 



FIRE SAND, NO. I. 



Below the Woodbridge clays there occurs a bed of quartz sand, 

 much of which is so angular in grain and so free from other 

 minerals as to be dug extensively for foundry and fire sand, as well 

 as for building purposes. Locally it contains thin beds of gravel, 

 and towards its base it carries lenses or seams of clay. The upper 

 portion of this sand bed is occasionally penetrated in the deepest 

 pits in the Woodbridge fire clay, but it is best exposed at the 

 numerous localities south of Bonhamtown, and south and east of 

 Milltown, where it is extensively dug. It is, also*, well exposed in 

 the upper part of many of the clay banks near Bonhamtown, 

 which go down to the underlying fire and terra-cotta clays. 

 Xcrth of the Raritan river it outcrops somewhat extensively east 

 of Mill brook and south Bonhamtown. It also forms a well- 

 defined belt south of the Raritan from the "Island farm," near 

 the mouth of Lawrence brook, southwest past Milltown and 

 Hoey's schoolhouse. The numerous localities at which this sand 

 bed has been opened are indicated on the map, Plate XL 



