Doc. No. 9.] 71 



on either hand transversely to its line of strike ; it is not unfrecyient that 

 the high angle of dip in the first instance will assnme a nearly horizon 

 tal position in the distance of a mile from the point of uplift, but the 

 next ridge will present a re-enactment of the first case if the rocks com 

 posing it are of the same character. 



The vertical position of the slates is one of those peculiar features 

 which attracts the attention of almost every person passing to or from 

 the interior, from their appearance resembling an old church-yard they 

 have been termed the grave-stone slates, and this distinctive feature is 

 found to pervail to the lower range of foot-hills toward the valley, as 

 well as in the more elevated parts of the mountains ; this vertically 

 among the lower hills has been urged as an objection to the point that 

 the intrusion of the quartz of either group, was not the immediate cause 

 of that uplift, but that the present inclination has been given by causes 

 of a a similar character which have acted subsequent to the intrusion of 

 the quartzose veins. 



This proposition seems invalid for this reason : if any such agency as 

 that proposed had been the immediate cause of producing the effects 

 which are observable among the slates of this section and sufficiently 

 powerful to have forced them into the position they now occupy ; it 

 seems but reasonable to suppose that some portions of the intrusive 

 materials should make their appearance among them ; but this is 

 not the case, nor is it necessary to introduce such a complication in order 

 to explain the physical features which are apparent in these rocks, as we 

 find an agent distributed largely among them, which is fully adequate 

 to induce all the changes of position or structure noticeable. 



That we do not find massive outcrops of these dikes among the slates 

 at the edge of the valley, is equally invalid as an objection against their 

 agency in producing the disturbances which are cleanly attributable to 

 their intrusion a few miles farther to the east, for an examination will 

 convince the unprejudiced mind that the causes which have been instru 

 mental in tilting the slates from their former position in the interior has 

 extended to the eastern edge of valleys and produced the ruptures we 

 there witness. 



In favorable situations for observing the intrusive character of the 

 recent group, as in the canons through which flow many of our streams 

 it is there found that the porphiries which lie superior to the primitive 

 rocks, and have had their origin from contact with igneous rocks in an 

 incanderescent state, as well also as the trapean rocks adjoining, are 

 broken through the sedimentary rocks above them which are still un 

 changed. 



Another fact of interest, and having an important bearing on this 

 part of our subject is found on the west borders of the great valleys and 

 in the Coast Mountains. From all the testimony in our possession at 

 the present time relative to the sedimentary rocks which dip under . the 

 valleys of the Sacramento and San.Joaquin, we are induced to believe 

 that those which occur on the east border are of an age cotemporaneous 

 with those on the west, and in addition thereto a group is found which 

 evidently belong to a still later period. We have in *these mountains 

 then, a corroborative evidence that the disturbances produced by the 



