Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/231

 of that author are well known, and I believe that in this country it is not necessary to enter into any refutation of his conclusions. As far indeed as the appearance of the trap rocks and their peculiar mineralogical character are concerned, the Huttonian theory offers an explanation better able to fulfil the requisite conditions than his hypothesis. I shall therefore decline entering into a comparative statement of systems so well known, or investigating the solidity of the examples which the French geologist has adduced from Great Britain. Although never formally discussed, the arguments and objections are familiar to most of those who have engaged in geological researches, and a full examination of his individual cases would lead into a dissertation foreign to the purpose of this notice, I may therefore briefly remark that the chief part of the hill in question consists of trap, which, like the other rocks of this family that alternate with secondary strata, is known in the Wernerian nomenclature, by the term of flœtz trap. I do not pretend to name its rank in the several formations enumerated under this general title, as I much doubt if the assigned characteristics are constant. If they are universal it will not be difficult to give it its place in the system when I have described its features and connections.

The phenomena which are most interesting in this hill render it necessary to take a range somewhat wide before describing the rock itself, without which we should be unable to trace its connection with the neighbouring rocks and the surrounding country.

Those who are acquainted with the mineral geography of Scotland know that a great portion of its northern district is separated, in many places very accurately, by a tract of breccia from the secondary rocks which occupy its middle portion. An irregular line drawn through Troup head, Dunnotter, Blair gowrie, Delvin,