Notes on the petrology of Arthur’s Seat

Abstract

As a previous paper in which I refer to the controversy recently raised as to the structure and age of this hill by Professor Judd, has been characterised by Professor Bonney as obscure in its petrology, I now desire to make my meaning plain. I. The hypothetical structure of a single or double volcanic neck, given in the various published diagrams of Arthur’s Seat, also involves more than Hutton’s postulate that its whinstones are identical with modern lavas, only of a submarine origin. The absence of sulphur from the neighbourhood, and the abundant presence of carbonate of lime in the rocks, appeared to demand the latter theory. Sir James Hall’s elaborate experiments on the changing of limestone into calcite by heavy pressure, were counted no less necessary buttresses of the Huttonian theory, than his other set of trials in fusing the rocks of the hill to watch the varied species of whinstone caused by different degrees of cooling. If modern Huttonists join with Rose and Percy to question the value of the pressure experiments, they cannot assume that the second set alone prove their case. The argument from general external form is not strong for the hill being a volcanic neck. The stone lion couchant differs from North Berwick Law for instance. Its unique physiography, even at first sight, appears to demand some other cause. Pursuing this argument of external form into special detail, recent observers maintain a strong resemblance with the volcanic ‶puys″ of Auvergne. The columnar structure of