402 



University of California. 



[Vol. i. 



tions from the normal arise from excess of matter and are associated 

 with uplift. The Appalachians and Rocky Mountains and the 

 Wasatch Plateau all appear to be of the nature of added loads, the 

 whole mass above the neighboring plains being rigidly upheld. 

 The Colorado Plateau province seems to have an excess of matter, 

 and the Desert Range province may also be overloaded. The fact 

 that the six stations from Pike's Peak to Salt Lake City, covering 

 a distance of 375 miles, show an average excess of 1,345 rock-feet, 

 indicates greater sustaining power than is ordinarily ascribed to the 

 lithosphere by the advocates of isostasy." * Elsewhere the same 

 writer remarks: "These results tend to show that the earth is able 

 to bear on its surface greater loads than American geologists, myself 

 included, have been disposed to admit. They indicate that unload- 

 ing and loading through degradation and deposition can not be the 

 cause of the continued rising of mountain ridges with reference to 

 adjacent valleys, but that, on the contrary, the rising of the moun- 

 tain ridges, or orogenic corrugation, is directly opposed by gravity, 

 and is accomplished by independent forces in spite of gravitational 

 resistance. 



" While the new data thus indicate that the law of isostasy does 

 not obtain in the case of single ridges of the size of a large moun- 

 tain range, they agree with all other systems of gravity measure- 

 ments in declaring the isostasy of the greater features of relief." f 



A paper by Reade,J which appeared at the end of 1895, is note- 

 worthy as evincing a change of view in admitting to a certain extent 

 the theory of isostasy.. Speaking of the pre-Permian Palaeozoic 

 strata, he remarks: "This loading doubtless squeezed and shifted 

 laterally some of the deeply lying and more mobile matter underly- 

 ing the normal crust, until a balance of stability was attained." He 

 insists, however, that this theory, "so insisted upon by American 

 geologists," is in noway applicable "to explain the compression, 

 folding, and building up of great masses of sediment into mountain 

 ranges. "§ 



* Loc. cit., pp. 73, 74. 



tjournal of Geology, Vol. Ill, pp. 331-334. 



X British Geology in Relation to Earth Folding and Faulting, Geol. Mag., 

 dec IV, Vol. II, pp. 557-565- 

 '/.Loc cit., p. 564. 



