392 



University of California. 



[Vol. i. 



equally palpable." Dutton, while inclined to regard denudation and 

 deposit as the active causes of elevation and subsidence respectively, 

 nevertheless realizes the necessity of appealing to something else to 

 initiate the differential movement, namely, "that mysterious plutonic 

 force which seems to have been always at work and whose opera- 

 tions constitute the darkest and most momentous problem of 

 dynamical geology." In the following year he states that in the 

 plateau region of Utah sediments from 6,000 to 15,000 feet in thick- 

 ness have been deposited over an area of more than 100,000 square 

 miles, and reveal the fact that at no time was the upper stratum far 

 from sea-level. The strata sank as they were deposited. It is sug- 

 gested that the displaced sub-crustal magma flowed under the ris- 

 ing Wasatch and Uinta Mountains and beneath the Great Basin.* 



The theory of the earth's crust so ably expounded by the Rev. 

 Osmond Fisher is now too well known to require any recapitulation 

 here. It is enough to say that it is closely bound up with the 

 hypothesis of a sensitive crust rising and sinking under varying 

 loads, and has undoubtedly been influential in giving prominence to 

 that view. He says in brief: "The exciting cause of the movements 

 of the crust, as we have attempted to explain them, is the transfer- 

 ence of sediment. Wherever that goes on, movements of the crust 

 may be expected to take place. And, although not altogether con- 

 fined to these regions, it is obvious that in continental areas, and 

 along their shores, these processes are the more energetic"! 



It is interesting, in view of the manner in which geologists have 

 been content simply to hold opposite theories on this question, to 

 compare Dutton's general statement in 1879, as to the consensus of 

 geological opinion in regard'to subsiding sedimentary tracts, with 

 one made by W. O. Crosby, J only four years later, in which he says, 

 "Geologists do not now generally believe that the profound sub- 

 sidences permitting the deposition of thick sedimentary formations 

 are produced by these same sediments." Truly a remarkable revo- 

 lution of general opinion, for which, however, we have no further 

 evidence than the two opposing statements themselves. 



* Geol. High Plateaus of Utah, Washington, 1880, p. 13. 



f Physics of the Earth's Crust (1881), pp. 221, 222. 



% Origin of Continents, Geolog. Mag., Vol. XX, pp. 244, 245. 



