CLAYS OF MIDDLESEX COUNTY. 435 



This is due to several causes. In the first place the workable 

 clays are confined chiefly to' the eastern and northeastern portions 

 of Middlesex county, in a rectangle with Cheesequake creek and 

 New Brunswick on its east and west respectively, and Menlo Park 

 and Old Bridge on its northern and southern boundaries. Within 

 this area there are found a great variety of clays ranging from 

 common brick clays up to- those of a very high grade of refrac- 

 toriness. 



A second reason for the prominence of this area lies in the 

 topography. There are many hillsides and valleys along which 

 the later gravel deposits are not so thick as on the hilltops and the 

 flatter country to the south. Hence the mining' and search for 

 clay deposits is facilitated. In this respect the Middlesex county 

 area stands out in strong contrast to regions farther southwest. 



Commercial advantage, by virtue of its position, is a third 

 reason for the prominence of the Middlesex district. Many parts 

 of the field are traversed by waterways, along which at many 

 points large factories have been erected, and, in addition to this, 

 most of the clay pits are in close proximity to- them as well, thus 

 permitting easy shipment by water to many coastal points. The 

 region is also crossed by several important lines of railroad. 



All these factors combined have helped to make the Middlesex 

 district one of the most important clay-working areas not only 

 of New Jersey but even of the United States. 



CLAY-BEARING FORMATIONS. 



Outside of the important clay-producing area in northeastern 

 Middlesex county, there are two- small ones. One of these is at 

 "Ten Mile Run, where an outlier of the Raritan formation is 

 -worked for terra-cotta manufacture. The other is a bed of Clay 

 Marl II at Jamesburg, and is worked to a small extent by the 

 Reform School, for brickmaking. 



We thus see that the Raritan is practically the only clay-bear- 

 ing formation as yet utilized in Middlesex county, although small 

 -quantities of loamy clay may be found in the Pleistocene deposits, 

 and Clay Marl II is used in a small way as already mentioned. 



As the stratigraphy of the Raritan clays has been described in 

 some detail in Chapter VIII, it will be sufficient here simply to em- 



