on Quartz Rock. 275 



the nature and disposition of this rock. Here it is disposed in thin 

 beds, rarely exceeding a few inches in thickness, and is inclined 

 towards the east in an angle of about 26 degrees. These beds 

 are divided by natural joints, at angles with the plane of stratifi- 

 cation, and in consequence of this they break into prismatic rhom- 

 boidal or triangular fragments, which on the upper and long-ex- 

 posed surfaces are so numerous and minute that the whole presents 

 at first sight a set of sharp points and projections, among which 

 the stratified disposition is scarcely perceived until they are more 

 closely examined. The same disposition into thin strata is every 

 where found throughout the larger masses, and if sometimes more 

 obscure, it can nevertheless be always discovered by an attentive 

 examination. 



"With respect to the composition of this rock it is almost always 

 found to be a compact splintery quartz, scarcely distinguishable in 

 small fragments from that mineral as it occupies veins. Occasion- 

 ally it becomes more or less granular, and now and then will be 

 found to contain grains of felspar, as it does in so many other 

 places. Its prevalent colour is white, but it sometimes assumes a 

 rusty colour at a small depth from the surface, and in some rare 

 instances may be observed of a pink and of a brown-reddish hue. 



If there is any transition between this rock and those with which 

 it is associated, it must be sought among those beds which approach 

 to a granular structure, between which and the most compact 

 varieties of the red sandstone the difference is not extremely great. 

 I cannot say that I have positively ascertained such a transition, 

 nor am I aware that the nature of the ground is such as to admit 

 of an examination sufficiently connected and extensive to answer 

 thus purpose. I shall however point out to geologists that part of 



