REVIEWS 333 



general use. Chapters III and IV include a discussion of the surface feat- 

 ures which lead to the identification of strata and structural conditions; 

 the methods of obtaining and recording geologic data; also the actual 

 field procedure from the selection of the field party to the preparation 

 of the final reconnaissance or detailed report. 



The statement is made (p. 129) that "the field work of a petroleum 

 geologist is ... . made up largely of a search for anticlines and terraces, 

 and of mapping such areas." This statement would have been more 

 nearly correct a few years ago. 



The book contains a glossary of about four hundred words, such as : 

 Algonkian, Carboniferous, Cenozoic, Contours, Dip Slope, Orientation 

 Rod, Stadia, Sedimentation, Volcanic Ash. There is also an appendix 

 containing tables of natural functions, reductions of stadia observations 

 for rod readings of 100, stadia tables for obtaining differences of eleva- 

 tions, gradienter table (Stebbinger drum) for determining distances, and 

 a number of other tables, including barometric corrections. 



A limp leather binding and pocket size make the book convenient 



for field use. 



■__ W. O. G. 



Lithologic Subsurface Correlation in the "Bend Series" of North 

 Central Texas. By Marcus I. Goldman. U.S. Geological 

 Survey, Professional Paper 129 A, 1921, Govt. Printing Office, 

 Washington. Pp. 22, pi. i, fig. i. 



Since the early work of Hatch, the micro-petrology of sediments 

 remained a rather neglected field to which the physiographer has only 

 turned now and then in the exceptional instances when there was a 

 question whether a certain sand was wind- or water-laid, a field almost 

 wholly ignored by the stratigrapher. Now the subsurface lithologic 

 correlations in oil fields have assumed economic importance, however, 

 interest in the long-neglected subject is revived, and geologists are glad 

 to learn of the establishment by the U.S. Geological Survey of a labora- 

 tory devoted to the study of sediments. The paper here reviewed 

 represents an invaluable addifon to the technology of petrographic 

 correlation from well logs and well samples. 



The problem presented was the correlation of sediments thought to 

 be the equivalents of the Smithwick and Marble Falls beds and of a 

 part of the Strawn formation of Pennsylvanian age, as well as of the 

 Lower Bend Series (Mississippian) in north central Texas. The method 

 employed was much like that outlined by Trager (Econ. GeoL, XV, 1920) ; 



