312 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Point, as seen from near North Dome, appears to have 

 formed along a set of diagonal or inclined joints which dip 

 east about 45°. 



Horizontal Joints. — Joints approximating in position to 

 horizontality are to be noted at many places. They are 

 especially well seen on the north side of the valley near 

 Yosemite Creek. Here two terraces clearly marked by 

 lines of trees have resulted from unequal erosion along hor- 

 izontal joints. At the base of the upper Yosemite Falls 

 is another terrace, and to the east of the falls, near the top 

 of the cliff, may be seen a series of nearly horizontal white 

 granite (aplite) dikes in granodiorite. These dikes were 

 doubtless intruded along the same horizontal joint sys- 

 tem. 



As has been before noted, the benches over which the 

 river tumbles at Nevada and Vernal falls are formed by 

 unequal erosion along horizontal joints, some of which may 

 be seen on the face of the cliff near the top of the Nevada 

 Falls. 



Relation of Joints to Schistosity. — Along some of the 

 joint planes, as for example those at "the Fissures," the 

 rock has been sheared, producing an incipient schistosity , 

 which may be related to the vertical jointing. In general, 

 however, the schistosity, where strongly developed, shows no 

 relation whatever to the joint planes. Thus the granodiorite 

 of the ridge east of Yosemite Creek and of Glacier Point 

 was evidently rendered schistose prior to the development 

 of the main system of joints, for these cut directly across 

 the schistosity. 



12. Formation of Domes. 



No one who has visited the southern Sierra can hav e 

 failed to be struck by the magnificent granite domes which 

 here and there stand above the general level. Fairview 

 Dome (Plate XXXVII) is an excellent example. It lies just 

 south of Tuolumne Meadows and is about 9,700 feet high, 

 or 1,200 feet above the meadows. In the view it is apparent 



