372 A. KEITH OUTLINES OF APPALACHIAN STRUCTURE 



this can only be made in the proximity of sediments which fix the rela- 

 tive position of the surface of the earth. Much detailed work is also 

 required, and a considerable separation of the Precambrian into different 

 formations must be possible. These three factors are best combined, so 

 far as now known, in western N"orth Carolina. In that region the great 

 border thrust faults have brought up the most deeply buried masses in 

 the Appalachians. These have been stretched and sheared along count- 

 less planes which approximate the horizontal over large areas. The 

 amount of actual horizontal motion as determined by the elongation of 

 crystals is as great as 10 to 1. In this single instance, therefore, the 

 deeply buried rocks do have low angle partings. It is, of course, not safe 

 to generalize from this instance, but it is clear that such a condition 

 exists in places, and it may be general. 



If horizontal partings in the lower portion of the crust are general, 

 the effect of this on the transfer of magmas is obvious. The easiest path 

 for the magmas would there be in a horizontal direction, without much 

 lifting of the entire erust. In that way might be explained the similarity 

 of batholiths over enormous areas — a fact which is apparent in the Appa- 

 lachians, and which has been noted in many parts of the earth. Such 

 horizontal planes would lead naturally in the upper layers of the crust 

 to the more highly inclined planes which we now observe. No break 

 would be expected between the horizontal and the inclined planes, and 

 therefore none between major batholiths extending horizontally at depths 

 and those which extend upward at high angles toward the surface. Such 

 a general arrangement, while of course highly speculative, meets the 

 general requirement of the observed facts and is easily within the general 

 possibilities. 



INCLUDED GASES 



There are two additional phenomena in connection with the intrusion 

 of batholiths which doubtless lend their assistance in causing some of 

 the phenomena of mountain-building. These are the explosive power of 

 gases and the j^ressure of growing crystals, both being directly connected 

 with the gain or loss of heat. The presence of gases in igneous rock has 

 long been known, and sufficient evidence of their existence and tremen- 

 dous force is seen in the explosion of volcanoes. In recent years it has 

 been determined that the explosions are due to steam and that the lavas 

 have a considera])le content of water. It has also been known that gran- 

 ites, the principal rock of batholiths, contain an appreciable amount of 

 included water. This is shown not only by direct inclusions of water in 

 crystals, but on a large scale by the solutions which pass from granites 



