HOMOCLINE AND MONOCLINE 91 



found in all three of the succeeding editions of A. Geikie's textbook, in J. 

 Geikie's Structural and Field Geology (1905), in the Standard Dictionary. 

 (1S95), in Webster's New International Dictionary (1910), Murray's New 

 English Dictionary (1908), in Norton's Elements of Geology (n. d., 1905?), 

 Scott's Introduction to Geology (1911), in Blackwelder and Barrows' Elements 

 of Geology (n. d., 1911?), and in Tarr and Martin's College Physiography 

 (1914). 



Several authorities define the adjective "monoclinal" in the sense of W. B. 

 and H. D. Rogers — "dipping in one direction" — while defining "monocline" in 

 the way adopted by Dutton and Geikie. Examples are to be seen in the Century 

 Dictionary (1895) and in Murray's New English Dictionary (190S). J. D. 

 Dana at first defined both "monoclinal" and "monocline" in the Rogers sense, 

 but in the last edition of his Manual of Geology restricted the meaning of 

 "monocline" as Dutton and Geikie had done. 6 



Among recent writers who have retained both "monoclinal" and "monocline" 

 in the broad Rogers sense are: R. S. Tarr (Elementary Geology, 1897), Cham- 

 berlin and Salisbury (Geology, Volume I, second edition, 1906), Anderson and 

 Pack (Bulletin 603, United States Geological Survey, 1915), and R. H. Johnson 

 (Science, volume 42, 1915, page 450). 



Favored Definition of "Monocline" 



It is safe to conclude that the majority of influential authorities writing 

 since 1880 have favored the Dutton-Geikie definition of "monocline." So far 

 as the writer has been able to find out, Dutton had the priority in the use of 

 this word in geology, while A. Geikie seems to be the first to have given it 

 formal definition. Therein lies one reason for retaining this usage. 



A second and stronger reason is found in the need for the word in just the 

 sense implied by Dutton and expressed by Geikie. For the observer working 

 in Arizona, Dutton's "monocline" is as necessary as "anticline" is for the 

 worker in Pennsylvania. In general, the geologists who are interested in a 

 simple, ultimately complete system of names for all types of folds may well 

 favor the Dutton-Geikie usage. The use of the noun in that sense makes 

 obviously desirable a similar narrowing of the adjective "monoclinal." This 

 seems to be a compelling argument for disregarding priority in connection with 

 "monoclinal" and for re-defining it so as to cover one instead of many kinds 

 of structure in bedded rocks. 



French and German authors have long used the word "flexure" (Flexur) to 

 signify "monocline" in the Dutton-Geikie sense. This usage was introduced 

 by Suess and followed by Richthofen, de Margerie and Heim, Reyer, Neumayr, 

 Credner, de Lapparent, and Haug. It is, however, impossible for writers of 

 English to limit "flexure" in this way. The word has too long meant "folding" 

 in general, or simply "fold," as in the writings of the Geikies, Prestwich. Jukes 

 Brown, W. B. and H. D. Rogers, Dana, Dutton, Willis, and others. Suess 

 proposed the restriction of meaning because the monoclinal fold (a result of 

 tension and radially acting force) was thought to be genetically and thoroughly 

 contrasted with anticlines and synclines (results of compression and tangential 



9 J. D. Dana : Textbook of Geology, 1864, p. 42 ; New Textbook of Geology, 4th ed., 

 1883 ( ?) ; Manual of Geology, 4th ed., 1895, p. 102. 



