394 



University of California. 



[Vol. r. 



ceding the deposition of the latter, and asks whether we are to 

 consider the three beds of sediment which often succeed a layer of 

 coal in the coal measures as being sufficient to cause the subsidence 

 that certainly took place during their deposition. Gardner* states 

 that the depression of the earth's crust by sediments, and the eleva- 

 tion of the same on the removal of weight, are facts which can not 

 be disproved. He recapitulates the original idea of Herschell of 

 the displacement of the subcrustal magma by the addition of sedi- 

 ments to the crust above it. Lastly, Professor Le Conte f recalls a 

 paper read by himself in 1859, before the American Association, in 

 which the continents are regarded as floating upon an interior 

 liquid magma and rising higher as lightened by erosion. His 

 position in 1884 is summed up in the following sentence: "That 

 loading and unloading the crust is a cause of subsidence and eleva- 

 tion there is little doubt, but that there are others and far more 

 important causes is certain." 



Dutton,! in 1884, emphasizes the enormous bulk of Mauna Loa, 

 and states that the whole mass has been rising while lavas have 

 been piling up. He suggests that regional elevation and volcanic 

 action are probably due to the same cause. The former is caused 

 directly by an expansion or by an increase of mass — probably the 

 former. Mauna Loa " floats high" because it is light, the upper 

 part being spongy and the lower part hot. 



In his" Origin of Mountains," published in 1886, Reade says that 

 '"bendings of the earth's crust initiated in other ways may be 

 increased by loading, but that the crust responds in a perceptible 

 way to every additional foot of strata laid down upon it is too great 

 a refinement to be possible."^ He conceives that the piling up of 

 ten miles of sediment might displace those benenth by flowage 

 under the enormous pressure, and refers to a probable connection 

 between sedimentation, subsidence, and earthquakes. As opposed 

 to unloading being the cause of elevation, he cites the well-known 

 fact "that the whole of an elevated region eventually gets leveled 



*-I6td, pp. 587- 588. 



t Ibid, Vol. XXIX, pp. 212, 213. 



+ Hawaiian Volcanoes, 4th An. Rept. U. S. Geol. Surv., pp. 190-195. 

 2 Origin of Mountains, p. 272. 



