Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/482

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Dr. Mac Culloch on Quartz 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 compact sandstone (since it may be often better described by this appellation) as the softer and better known breccias occurring on the borders of the flœtz 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 exhibit 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 alternate 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 adoption of the word primary, in lieu of primitive (a change already recommended) removes this apparent contradiction, since it is only