498 



DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



This fact of downward enlargement makes it still more surely impossible 

 to conceive that the granodiorite was injected into the sediments by filling a 

 cavity opened by orogenic energy. A visible section even 2,200 feet deep does 

 not prove the continuance of downward enlargement with depth; yet there is no 

 logical reason to doubt that at least the steeper observed dips of the igneous 

 contact surface are but samples of its dips for several miles beneath the present 





Figure 39. — Plunging contact surface, Castle Peak stock, south side, near point "D", 

 Figure 35. View loojuug east. Granodiorite on left of line showing contact. The ver- 

 tical distance between the two ends of this line as drawn is 800 feet. The highest 

 summit is Castle Peak. 



land surface. Moreover, if the granodiorite made its own way through the 

 stratified rocks and was not an injected body, passively yielding to ordinary 

 orogenic pressures, there must have been free communication between the now 

 visible upper part of the magma chamber and the hot interior of the earth. 

 Downward enlargement is not only proved in visible cliff sections; it is 

 demanded as a necessary condition of heat supply during spontaneous intrusion. 



