xxiv PREFACE. 



chemical properties of clay. In Part II the stratigraphy of the 

 New Jersey clay deposits is considered, and the geological forma- 

 tions of the State which contain workable clays are described. 

 Brief mention is made of all the worked deposits, reference being 

 made to the maps by locality numbers. In Part III the methods of 

 manufacture of the various classes of clay products are discussed, 

 with particular reference to- New Jersey methods. No attempt is 

 made to describe individual plants for two reasons. No advan- 

 tage was to be gained by repeating details of manufacture, where 

 commonly accepted methods were employed and similar types 

 of machinery used, and on the other hand it was felt that all 

 manufacturers had a right to' have their trade secrets, in so far 

 as they had any, respected and preserved inviolable. Inasmuch 

 as the technology of the pottery industry, particularly of the 

 higher grades, is exceedingly complex, its full treatment would 

 transcend the limits of a report of this character. Moreover, inas- 

 much as comparatively little New Jersey clay is used in the higher 

 grades of pottery ware, in which flint and feldspar are large 

 ingredients, it was thought best to restrict the chapter on pottery 

 to somewhat narrow limits. In Part IV the economic geology 

 of the New Jersey clays is considered, and they are discussed, first 

 by formations, their physical and chemical characters being sum- 

 marized, and then by counties. In this chapter mention more or 

 less brief is made of all the clay deposits of the State, so far as 

 known. In the case of those districts, however, where the clays 

 have been worked for many years, and clay banks are so frequent 

 that descriptions of each bank would pad the report unnecessarily, 

 only the most important banks or the more representative types 

 of clay have been tested and described. 



In preparing the report the endeavor has been to make it of 

 interest and value to all clay workers. The fact has been recog- 

 nized that the great majority of them are not thoroughly familiar 

 with chemical and geological terms. It has not been possible, 

 however, to avoid the use of these, but the endeavor has been 

 made either to explain them when first used, or to use them in 

 such a way that their meaning is apparent. For this reason, also, 

 the use of chemical symbols, unless accompanied by their names, 

 has been avoided as far as possible. 



