MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 165 



marbles, he noted the important fact that they were all more or less adjacent to the 

 mass of red felspar rock on Cnoc-na-Sr5ine or its branches, and he further made the im- 

 portant deduction that the marble is merely a portion of the limestone series of 

 Assynt.* But while giving weight to these observations, he was inclined to the opinion 

 that the red rock of Cnoc-na-Sr5ine is a mere variety of the " Logan Rock." 



Near the south-western limit of the Cnoc-na-Sr5ine mass Professor Heddle observed a 

 rock on the east bank of the Ledbeg River, at the bridge on the road leading to Elphin, 

 about which he makes the following statement. The rock " is highly characteristic, 

 though its characteristic features are possibly due to a modification of pseudomorphic 

 alteration. In structure it resembles the westerly dull-red bed of ' Logan,' but it 

 has a brown colour blotched with dull greenish-grey. It has a waxy lustre, is trans- 

 lucent, and the greater part of it cuts easily with the knife. It consists of a muddy dull 

 red felspar, in rude crystals, embedded in a substance which is identical in appearance 

 with the pseudophite from Plaben Budweis." t 



Again, to the east of Aultivullin and Loch Am Meallan, he was impressed with the 

 peculiar features of the rocks forming the main mass of borolanite. He observes that they 

 are " in appearance intermediate between that of Cnoc-na-Sroine and the ' Logan Rock,' 

 with here and there a great resemblance to the rock seen at the Bridge of Ledbeg ; at 

 other points there is some slight resemblance to an igneous rock. The rock of the east 

 end of the hill is again like ' Logan,' of a red hue, and a grey-brown labradorite-like 

 bed is the last seen." J 



In 1883, Dr Callaway made brief allusion to some of the igneous rocks in the 

 Assynt series, referring more particularly to the Loch Ailsh group, extending from 

 Ledmore to the gap south of Loch Ailsh. While noting the granitoid texture which is 

 characteristic of this mass, he called attention to an exceptional garnetiferous variety 

 occurring to the east of Loch Borolan, on the slope north of the road.§ In the appendix 

 to this paper, Professor Bonney describes the microscopic characters of a few specimens 

 of these igneous rocks, collected by Dr Callaway. IF Regarding the exceptional garneti- 

 ferous variety, he states that it is " a most perplexing rock. In the slide a fair quantity 

 of black mica is at once recognised, and a number of subtranslucent sap brown garnets, 



the larger (being the less regularly formed), including flakes of mica, &c The 



ground of the slide appears to consist partly of a felspar, in patches of a most irregular 

 form (with perhaps a little quartz), and a mineral which occurs in rather wavy bunches, 

 like tufts of long thread or rootlets, or a kind of ' canal system.' It seems to have re- 

 placed the felspar, and may be one of the fibrolite group." 



One of the dykes in the Traligill Burn near Inchnadamff is described by Professor 

 Bonney as a hornblende porphyrite. 



In 1886, one of the authors of this paper published notes on some hornblende-bearing 

 rocks from Inchnadamff, containing a description of the rocks and the characters of the 



* Min. Mag., vol. v. p. 274. + Mineralog. Mag., vol. v. p. 294. % Mineralog. Mag., vol. v. p. 295. 



§ Q. J. G. Soc, vol. xxxix. p. 409. IT Q. J. G. Soc, vol. xxxix. p. 420. 



