Reviews. 



The Clays and Clay Industry of New Jersey. By Heinrich Ries 

 AND Henry B. Kummel, assisted by George N. Knapp. 

 (Geological Survey of New Jersey, Vol. VI.) Pp. xxi + 548; 

 LVI plates, and 41 figures in text. 



In 1868 the Geological Survey of New Jersey, Professor George H. 

 Cook, state geologist, published a full report on the clays of the state — a 

 report which was of great service in its day. Ten years later a further 

 report on some of the more important clay districts of the state was issued. 

 These earlier reports were long since exhausted. Furthermore, the develop- 

 ment of the clay industry and the progress of knowledge of the geology of 

 the state, have created a demand for the new report on the clays of the 

 state. The present volume is in response to this demand, and brings the 

 subject up to date. 



The importance of the clay industry in New Jersey is shown by the fact 

 that in 1902, the last year for which statistics are available, the total value 

 of the clay products of the state was more than $12,600,000. 



The economic phases of the subject are primarily the work ot Dr. 

 Ries, while the geological questions involved are primarily the work of Dr. 

 Kummel, who, however, has availed himself of the data in possession of 

 Mr. Knapp, who became familiar with the Cretaceous and later strata of 

 the state in connection with his work on the Pleistocene of southern New 

 Jersey. 



The volume is divided into four parts as follows: (i) Clay 'and its 

 Properties, including a discussion of the occurrence of clay, the methods 

 by which it is worked, as well as its physical and chemical properties (pp. 

 1-115); (2) "Stratigraphy, the clay of the state being foimd in various 

 formations, chiefly in the Cretaceous, Tertiary, and Pleistocene (pp. iig- 

 203); (3) The Manufacture of Clay Wares, which include brick, fire- 

 brick, terra cotta, wares for structural work, tile and pottery (pp. 205-342); 

 (4) The Economic Geology of the New Jersey Clays pp. 343-508). To 

 these four parts are added appendices giving statistics of clay production, 

 bibhography of clay literature, and tables of chemical analyses and physical 

 tests. This outline of the contents of the volume gives an adequate idea 

 of its scope. 



562 



