PREFACE. xxiii 



190 1 upon a new report, which should consider not only the 

 known and developed clay deposits, but which, so far as possible, 

 should contain definite and practical information concerning 

 unworked beds, which future demands may render profitable. It 

 was felt, too, that a new clay report should consider more in 

 detail the technology of the clay industry, and so 1 be of value not 

 only to the miners of clay, but also 'to' the manufacturers. 



The present volume is the result of the work commenced in 

 1901 and continued, with some interruption, to the present time. 

 While three names appear upon the title page, it is but fair to 

 Dr. Ries to state that the general plan of the report is his. He 

 visited in the field nearly all the clay deposits noted and nearly all 

 the important clay-working' establishments. All of the physical 

 and some of the chemical analyses and tests, except the breaking 

 and crushing tests upon the brick, were made by him, and he 

 is the authority for the statements regarding the economic value 

 of the clays, as well as the methods of manufacture. 



For several years Mr. Knapp has been engaged in a detailed 

 study of the formations in southern New Jersey, and while his 

 work has not been primarily upon the clay deposits, nevertheless 

 he had accumulated a large amount of valuable information 

 regarding the occurrence of clay beds, which very much simplified 

 the task of locating undeveloped deposits. His studies also 

 assisted materially in the correlation of the clay deposits and their 

 reference to the proper geological horizon. The geological data 

 on the general map of the State, Plate X, and of the Alloway 

 clay, Plate XIII, were furnished mainly by him. 



The stratigraphy of the clay deposits has been the particular 

 work of the State Geologist, assisted, as above noted, by data 

 furnished by Mr. Knapp. He is also responsible for most of the 

 detailed mapping of the clay beds in the district from Wood- 

 bridge to Keyport, Plates XI and XII. Although Parts I and 

 III and Chapter XVIII of Part IV were written by Heinrich 

 Ries, Part II by H. B. Kiimmel and Chapter XIX of Part IV 

 conjointly, yet both authors have had the benefit of the others' 

 suggestions and criticisms. 



In the present report, in Part I, Dr. Ries discusses in consider- 

 able detail the origin, modes of occurrence and physical and 



