472 Dr. Mac Culloch on Qjtartz Rock. 



older schists are apparent in other places, I think future observations 

 will confirm my supposition that it is a member of this class of rocks. 

 A highly indurated breccia may be seen near Boharm, on the line 

 now described, consisting of angular fragments of red and white 

 quartz, so compacted that they do not separate from the bed on 

 breaking the rock, but the whole gives way together, as if it were 

 one continuous mass. The same rock now and then contains 

 jaspers dispersed through it in the form of fragments. As I have 

 observed similarly indurated breccias accompanying a similar quartz 

 rock in other places, I suspect that this breccia is a portion of the 

 same formation, bearing such a relation to this quartz rock, or com- 

 pact sandstone (since it may be often better described by this appel- 

 lation) as the softer and better known breccias occurring on the 

 borders of the floetz strata do to these latter. I also suspect that 

 greater simplicity of composition and more perfect induration will 

 be found to be leading characters of the breccias of this class, the 

 causes of which must be sufficiently obvious, and that portions of 

 breccia or large grained mechanical formation, will generally be 

 found accompanying the older schistose strata whenever these ex- 

 hibit the smaller grained mechanical disposition. It is to these that 

 the unfortunately constructed term of primitive breccias has been 

 applied. If we could securely adopt the names of breccias and 

 sandstones of transition, this contradiction in terms would be 

 avoided, but if as I have already shown, and shall presently I hope 

 more fully prove, the quartz rock under review does actually alter- 

 nate with the rocks called primitive, it is plain that we cannot 

 have recourse to this expedient, but must be content, if we use the 

 term primitive, to bear with the unseemly compound. The adop- 

 tion of the word primary, in lieu of primitive (a change already 

 recommended) removes this apparent contradiction, since it is only 



