Petrological Notes on the Vicinity of the Upper Part of Loch Maree

Abstract

The relations of the rocks on the western border of Ross and Sutherland have long been a subject of controversy. Into the details of this it is needless to enter on the present occasion, as they have been recently recapitulated to the Geologists′ Association and published in their Proceedings*. The materials for this sketch are mainly contained in our own Journal; and the last contribution to the subject was a paper read by Dr. Hicks on May 22, 1878†. After listening to the ingenious theory put forward by that author, it occurred to me that the question was one on which the testimony of the microscope ought to be especially valuable. According I spent some days last summer at Kinlochewe, in order to examine the rocks in the field and to obtain specimens for microscopic work. I have now the honour of laying before the Society the results of these investigations. (1) Syenite of Glen Laggan. Previous writers on the above section have agreed in stating that a mass of igneous rock makes its appearance on the floor of Glen Laggan, about two miles from Kinlochewe, and extends for some distance up the bed of the stream, apparently cutting off the quartzite from the newer group. This rock is called diorite by Nicol, syenite by Murchison, Geikie, and Hicks; it is shown by the last author upon a section‡ as intrusive among the calcareous series which overlies the quartzites. Almost immediately on reaching the spot where the “syenite” first appears