xxii PREFACE. 



The fact that the map of the same district accompanying this 

 report — Plate XI — differs from it in detail does not contradict 

 the above statement. The differences are more apparent than 

 real, and are due to the slightly different classification adopted. 

 Many clay beds, formerly thrown aside as worthless and not 

 included on Dr. Cook's map, have been delimited on the present 

 map. Then, too, the attempt has been made to indicate not only 

 the outcrop of each clay belt, but also its probable underground 

 extension, so far as it is not too deeply' buried by later deposits 

 to permit its being worked. 



Subsequent to the publication of the Report on Clays in 1878, 

 an exhaustive study of the fusibility of New Jersey clays was 

 made, as well as of all the important fire clays of other states and 

 foreign countries. The results of these tests were published in 

 the Annual Report for 1880. Owing, however, to the fact that 

 it was not considered practicable to determine the intensity of 

 the heat obtained, nor to measure the pyrometric effects, other 

 than as indicated by the fusing of platinum before the more 

 refractory clays were melted, these tests show only the relative 

 infusibility of the clays tried, and cannot be used in comparison 

 with the fusion tests in this report, where the conditions were 

 different and the temperature effects are indicated in terms of the 

 standard Seger cone numbers. 1 



In 1897 and 1898 a thorough canvass of the brick and clay 

 industries (not including pottery) of the State was made and 

 the results published in the Annual Reports of the State Geologist 

 for those years. It showed that. during 1898, 7,510 men were 

 employed, 403,711,708 brick were made, and that the total value 

 of the clay industry (exclusive of pottery) was $5,748,726. 



Requests are frequently received by the Survey for informa- 

 tion regarding the clays of the State, and, although a few copies 

 of the Clay Report for 1878 are still available for distribution, 

 yet it has been felt for some time that that volume did not fairly 

 represent the present condition of the clay industry, particularly 

 as there has been a marked development in the southern portion 

 of the State, a region almost entirely untouched by the earlier 

 report. xA.ccordingly, field work was commenced in the fall of 



1 Pages 101 et seq. 



