CLAYS OF MIDDLESEX COUNTY. 471 



as those used for common brick, i. e., the upper part of the Wood- 

 bridge clay bed. Several very large factories are in operation (see 

 Chap. XIV) at Perth Amboy, Keasbey, Sewaren, Spa Spring and 

 Maurer. The product of these consists almost entirely of hollow 

 Avare for structural and fireproofing work. In addition two 

 works at least are being run almost exclusively for the manu- 

 facture of conduits for underground electrical work. The fire- 

 brick industry (Chap. XVI) is an old-established one in this 

 county, as is but natural considering the vast quantities of refrac- 

 tory clays that have been dug and are still being dug here. Fire 

 brick and other refractory shapes are manufactured chiefly at 

 AVoodbridge and at several points along the Raritan river. Wall 

 tiles are made at Menlo Park, Old Bridge and Perth Amboy, but 

 the materials used are obtained mostly from, other States. Terra 

 cotta is another important product, and a growing demand for 

 this line of materials is supplied by three factories in the county, 

 all of them being at Perth Amboy. Paving brick are produced by 

 one factory at South River. 



The clay-mining industry has been treated in some detail in 

 Chapter XVII, and that should be referred to. The refractoriness 

 of New Jersey fire brick has alsoi been discussed in some detail in 

 Chapter XVI. 



Since the number. of manufacturers in this county is so great 

 they are not included here, but the reader is referred to the chap- 

 ters on common brick, terra cotta, fireproofing, conduits, wall tile, 

 floor tile and pottery (Chaps. XI-XVI), where the names have 

 been already given. 



