FOLDS AND FAULTING. 459 



vanced that in numerous cases the production of mountain 

 masses has been preceded by the deposition of great thick- 

 nesses of marine strata, thus giving weight to the theory 

 that a close connection exists between mountain elevation 

 and a geo-synclinal. Yet scarcely has a rule been es- 

 tablished, or an absolute tectonic creed promulgated, than 

 fact upon fact pours in, either to shake our faith, or test our 

 infallibility. Nothing seemed more certain than that the 

 Plutonist School had suffered complete defeat and anni- 

 hilation, yet in 1877 Gilbert (12) proved that there are 

 great intruded laccolites, extending many miles in a hori- 

 zontal direction, and that the stratified deposits overlying 

 them have not only been carried upwards by this vertical 

 movement, but have been raised a height of 5000 feet with- 

 out a trace of fracture, so that Von Buch's generalisation 

 failing to account for the greater, having been proved 

 essentially applicable to the lesser, and vertical pressure 

 once again claims its place as one of the formative 

 agents in mountain formation. 



Should we, again, be prepared to submit that, with the 

 exception of mountains formed of volcanic materials erupted 

 along a line of fissures, tangential compression has alone 

 been active, and that mountain ranges must of necessity 

 exhibit the complicated foldings referred to, we must again 

 halt, seeing that a region is now known in which folding, as 

 such, is entirely absent, Dutton and Powell having shown 

 that the High Plateau of Utah, and the Uinta Mountains 

 have been formed by faults, whose vertical throw has, in 

 some cases, exceeded 7000 feet, and instead of the strata 

 being waved, steep " monoclinal flexures " are produced. 



Do we hold that folding is in the main essential where 

 lateral pressure is active, we are face to face with Lory's 

 assumption that faulting must be the precedent condition 

 ere folding can be set up in mountain ranges. 



What we must now ask ourselves is — whether, in the 

 face of all these apparent counter-movements, the broad 

 principles of folding have been affected, and lost their 

 power or influence ? Whether their fruitfulness in sugges- 

 tion is exhausted, or whether their theoretical basis is strong 



