CLAYS OF SOMERSET COUNTY. 503 



SOMERSET COUNTY. 



With the exception of a small outlier of Raritan clay east of 

 Rocky Hill, all the clays worked in this county are of Pleistocene 

 or post-Pleistocene age. They are generally sandy and at times 

 even stony, but make an excellent common brick, judging from 

 the hardness and ring of the product, although no crushing or 

 transverse tests were made. 



Somerville. — The largest of the clay pits is 1 mile northeast 

 of Somerville (Loc. 234). The deposit is a red clay with numer- 

 ous pebbles in certain portions of it. Its origin has been dis- 

 cussed on p. 130. The run of the bank is used and there is no 

 stripping. 



The physical characters of the material are those of a good 

 brick clay. Thus it mixed up with 20.5 per cent, of water to a 

 mass having an air shrinkage of 5 per cent. The average tensile 

 strength was very high, being 297 pounds per square inch. 



At cone 03 the fire shrinkage was 5 per cent. At cone 1 it is 

 6.6 per cent., with an absorption of 0.64 per cent. The clay be- 

 came viscous at cone 8. It burns red and is worked up in a 

 soft-mud machine. The bricks which are probably not burned 

 above cone 05, show a linear air shrinkage of 7.3 per cent, and 

 a fire shrinkage of 3.0 per cent. The greater air shrinkage than 

 that obtained in the laboratory is due to their being molded softer. 



North Plainfield. — Another deposit of Pleistocene clay is 

 worked at the brickyard of D. Hand & Son, two> miles north of 

 Plainfield (Loc. 236). The clay itself is quite gritty but more 

 sand is added to it, so that the air shrinkage is extremely low 

 only 1.4 per cent., while the linear fire shrinkage is 5.8 per cent. 

 The cubic air and fire shrinkages are 11.5 per cent, and 7.3 per 

 cent., respectively. The clay burns red. . 



Dunellen. — At Rajotte's brickyard (Loc. 235) near Green 

 brook just north of Dunellen, Union county, a black flood-plain 

 and swamp clay is used. The clay is from 4 to 6 feet deep and 

 is underlain by glacial gravel. It is said to cover 14 acres. 



Rocky Hill. — Terra-cotta clay has been found east of Rocky 

 Hill (Loc. 299) at a number of points, several of which are 



