OB THE VICINITY OF THE UPPER PART OF LOCH MAREE. 93 



8. Petrological Notes on the Yicinitt of the Upper Part of Loch 

 Maree. By Eev. T. G. Bonnet, M.A., P.E.S., Sec. G.S., Pro- 

 fessor of Geology in University College, London, and Pellow of 

 St. John's College, Cambridge. (Bead December 3, 1879.) 



The relations of the rocks on the western border of Boss and Suther- 

 land have long been a subject of controversy. Into the details of 

 this it is needless to enter od the present occasion, as they have been 

 recently recapitulated by Mr. Eudleston in a luminous critical 

 sketch communicated 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 sub- 

 ject was a paper read by Dr. Hicks on May 22, 1878 f. After lis- 

 tening to the ingenious theory put forward by that author, it occurred 

 to me that the question was one on which the testimony of the micro- 

 scope 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 investiga- 

 tions. 



(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 dis- 

 tance up the bed of the stream, apparently cutting oiF the quartzite 

 from the newer group. This rock is called diorite by Mcol, 

 syenite by Murchison, Geikie, and Hicks ; it is shown by the last 

 author upon a section :J: as intrusive among the calcareous series 

 which overlies the quartzites. 



Almost immediately on reaching the spot where the " syenite " 

 first appears on the floor of Glen Laggan § I was struck with its 

 gneissic aspect. AVithout, however, halting for long, I walked up 

 the bed of the valley for about two miles, examining the rocks as I 

 went, and found this gneissic aspect continued. About 100 yards 

 from a cottage (perhaps three miles from Kinlochewe) there was indu- 

 bitable gneiss, the foliation dipping to about W. 30° S.|| Near the 

 junction of the two upper branches of the glen I climbed up the right 

 bank for about 300 ft., and found clearly marked foliation, dipping at 

 25° to about S.E. ; and about 50 ft. above this a well-banded gneiss 

 occurs, dipping 30° to about E. Still higher up I found a shaq^er 

 dip, rather to E.S.E.If 



* Vol. vi. No. 2. t Published vol. xxxir. p. 811. 



X Q. J. G. S. xxxiv. p. 814. § Glen Cruchalie of Murchison. 



II The readings were made with a pocket compass, subsequently corrected 

 to true. 



^ It may be well to mention that I am perfectly aware (see my paper 

 Q.J. G. S. vol. xxxiii. p. 893 &c.) that occasionally true igneous rocks exhibit 

 foliation. This possibility was always present to my mind during the exami- 

 nation of the above district ; but what I then saw seemed inexpUcable in that way. 



