304 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



tained by Professor Charles Lory, by Ebray and Magnan. 

 Professor Favre also dissented from the supposed vertical 

 uplift of the Alps. In 1867, in a now classic description of 

 the geology of Mount Blanc, he ascribed the complex fan- 

 shaped arrangement of the rocks in that mountain to the 

 action of strong lateral pressure. 



Important additions to the knowledge of mountain-struc- 

 ture were meantime being made by the North American 

 Geological Survey. In 1842, at a Congress of British and 

 American Scientists, H. D. Rogers had expressed his views on 

 the stratigraphical composition, the tectonical relations, and the 

 mode of origin of the Appalachian mountains. The one-sided 

 asymmetric arrangement of the folds in the Alleghanies, the 

 absence of any central axis consisting of crystalline eruptive 

 rocks, the fact that the whole mountain-system was composed 

 of numerous parallel folds, most of them curved in form, 

 could not in Rogers's opinion be brought into harmony 

 with the theories of mountain-upheaval which were at that 

 time current in Europe. He argued against the conception 

 that ascending eruptive masses uplifted superincumbent rock- 

 strata, and also against Prevost's opinion that mountains were 

 formed as a consequence of local inthrows and crust 

 subsidences. His own theory of mountain-folding supposed 

 the disturbing cause to be wave-like pulsations into which the 

 molten magma of the nuclear body was thrown from time to 

 time, when the accumulated tensions in the earth's thin crust 

 caused an actual rupture. The form, arrangement, and 

 inclination of the folded strata were ascribed to a combined 

 wave-like and tangential movement, which was also accom- 

 panied by an injection of eruptive masses into the cavities 

 created within the folds during the movement. 



Professor Dana 1 was the geologist who first gave clear ex- 



1 James Dwight Dana, born on the I2th February 1813 at Utica in 

 New York State, entered Yale University in 1833 and made a journey to 

 Europe during his college course. In 1838 he was selected as geologist 

 and mineralogist for the Wilkes Exploring Expedition, and during the 

 four years' voyage became acquainted with the coasts of South America 

 and the Pacific Ocean. Dana was shipwrecked off the coast of Oregon, 

 but fortunately succeeded in reaching San Francisco and sailed once more 

 by the Sandwich Isles, Singapore, and St. Helena to New York. 

 Thirteen years were then devoted to the examination and description of 

 his geological and zoological collections. His reports on the geology of 

 the Pacific Ocean, the volcanoes of the Sandwich Islands and coral reefs, 



