J. LeConte—Structure and Origin of Mountains. 99 
morecomplex. Renevier has recently shown* that the Vaudoise 
mountains in which the horizontal mashing has been extreme is 
probably in most cases, the result of an arch strongly pressed 
together at the base, spreading at the top by its weight, and per- 
haps broken by tension, and the whole powerfully eroded, as 
shown in the ideal diagram, fig. 8. This is the view now taken 
by Favre, by Lory, by Heim and Giordano and other Alpine 
geologists.+ A similar structure, however, may result also from 
the erosion of a closely appressed syncline, as shown in fig, 9. 
ee ee ee ee Payee crs a Sap 7 — > 
Ideal section showing how fan- Ideal section showing how fan- 
structure may be produced by structure may be produced by 
erosion of an anticline. erosion of a syncline. 
The kind of mountains just described and of which the 
Coast Range may be taken as the simplest type, is that which 
is always formed when the crust of the earth yields sufficiently 
easily to the horizontally-acting mountain-making force. 
course in such cases the whole mass of crumpled strata is 
usually drops, by gravitative adjustment, 
ur 
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