168 QnCKSILVEli DEPOSITS OF THE PACIFIC SLOPE. 



Consequent effects of upheaval. — Grranting, as oiie iiievitablv must, that there are 

 areas over whlcli there is a tendency to the prevalence of uplieavals over 

 subsidences, the laver of a supposed fluid interior of tlie globe whicli con- 

 gealed to-day on the under surfiace of the crust in such areas must rise 

 gradually or intermittently and will Ije exposed to the air at some remote 

 future period. Or if the globe is a viscous solid, the plastic mass beneath 

 the lowest sediments in areas of predominant upheaval must be rising to- 

 ward the sui'ffice. In either case it would appear from the above that the 

 exposure at the surface of the earth of material upon which no ray of liglit 

 has ever fallen since the outer layer of the earth congealed must be of daily 

 occurrence. 



Logical consequences of sedimentary hypothesis The SUppOSitiOU that all the material 



now exposed to view has passed through the sedimentary condition seems 

 to be conceivable only in one way. It implies the hj-pothesis that upheaval 

 and subsidence are substantially superficial phenomena, in which the inte- 

 rior of the earth has no part. It supposes that the sediments which subside, 

 off a coast perhaps, afterwards flow laterally and again ascend to the sur- 

 face at some other point, perhaps in a fluid or plastic state, as lava or granite. 

 This is a condition of things which cannot always have existed. The ])ri- 

 meval massive rocks must evidently have been exposed until the entiie 

 quantity of material which has ever been brought into the form of sedi- 

 ment was eroded from their surfaces, and, during that period, the interior 

 of the earth must have partaken in the movements of upheaval and subsi- 

 dence. The greater the quantity of matter which is assumed to have been 

 at some time sedimentary, the longer must the exposure of primeval nuiss- 

 ive rocks have continued and the more difficult does it become to under- 

 stand how the interior can ever have ceased to be aff'ected by upheaval and 

 subsidence. The geologists who take this view are compelled to assume an 

 enormous thickness for sedimentary material, and they must consequently 

 also suppose that primitive rocks have been exposed during an enormous 

 period. The fact appears to be, however, that the supposed failure of the 

 earth's interior, say beneath a mean depth of twenty miles, to partake in 

 the movements of upheaval and subsidence is totally inexplicable on 

 mechanical principles. Some geologists have hotly assailed physicists for 



