Barrel! — Growth of Knowledge of Earth Structure. 13 S 



deposition, in consequence of the setting of the current from the 

 opposite or southeastern shore." 



In 1842, at the third annual meeting- of the Association 

 of American Geologists both H. D. and W. B. Sogers 

 argued (43, 170, 1842) against Sir Charles Lyell and E. 

 Hitchcock that the present dip of the Triassic was the 

 original slope of deposition, stating among other reasons 

 that the footprints impressed upon the. sediments often 

 showed a slipping and a pushing of the soft clay in the 

 direction of the downhill slope. In 1858 H. D. Sogers 

 still held to the same views of original dip, 2 notwithstand- 

 ing that a moderate amount of observation on the mud- 

 cracked and rain-pitted layers would have supplied the 

 proof that such must have dried as horizontal surfaces. 

 The idea of inclined deposition is not yet wholly dead as 

 it has been suggested more than once within the present 

 generation as a means of escaping from the necessity of 

 accepting the very great thicknesses of this and similar 

 formations. Thus, as Brogger has remarked in another 

 connection, — the ghosts of the old time stand ever ready 

 to reappear. 



In the present essay on the rise of structural geology 

 as reflected through a century of publication in this 

 Journal, attention will be given especially to two fields, 

 that of structures connected with igneous rocks and that 

 of structures connected with mountain making, and 

 emphasis will be placed upon the growth of understand- 

 ing rather than upon the accumulating knowledge of 

 details. The growth in both of these divisions of struc- 

 tural geology is well illustrated in the volumes of the 

 Journal. 



Structures and Belationships of Igneous Rocks. 



Opposed Interpretations of Plutonists and Neptunists. 



During the first quarter of the nineteenth century the 

 geologic controversy between the Plutonists and Nep- 

 tunists was at its height; the Plutonists, following' the 

 Scotchman, Hutton, holding to the igneous origin of 

 basalt and granite, the Neptunists, after their German 

 master, Werner of Freiberg, maintaining that these 

 rocks had been precipitated from a primitive universal 

 ocean. The Plutonists, although time has shown them to 



2 H. D. Eogers, Geology of Pennsylvania, vol. 2, pt. II, pp. 761, 762, 1858. 



