638 MESSES. J. HOENE AND E. GEEENLY ON [Nov. 1 896,, 



to several yards or more in length. Their constituents resemble 

 those of the larger veins and sills already described. Immediately 

 to the west Mr. Peach has traced a great series of thin sills of 

 foliated granite traversing the biotite-schist and granulitic gneiss. 



Where the granitoid rocks traverse the biotite-schist or gneiss on 

 the moor about 2 miles south of Armadale, the contact-mineral 

 sillimanite was observed in the latter, associated with the biotite. 

 This mineral was likewise found in an inclusion of biotite-gneis* 

 in a granite-vein. The occurrence of the quartz in the biotite- 

 gneisses in large, almost ophitic patches may also point to contact- 

 metamorphism — if we may judge from an instance of the change 

 produced in siliceous gneiss at the point of contact with an intrusive 

 mass of augite-biotite-diorite at Sandside, Eeay, in Caithness. 



The foliated granite and the complex of gneisses between Kirk- 

 tomy and Armadale are traversed by veins of pink microgranite y 

 which, so far as observation goes, are never foliated. These veins 

 probably represent the last phase of igneous activity, which culmi- 

 nated in the introduction of the broad sills of foliated granite. 



Reference may now be made to some of the other groups of 

 crystalline schists represented in the area under consideration. 



Group 4, composed of hornblende-gneiss or schist, is likewise 

 traversed by gneissoid granite and pegmatite. It occurs in lenti- 

 cular bands or masses, which are represented on the eastern side 

 of Kirktomy Bay, and on the moor to the south-east. A specimen 

 from the eastern cliff of Geodh Acrah, J mile north of Kirktoray, 

 examined under the microscope by Mr. Teall, sho *vs felspar, mostly 

 striated, quartz, and green hornblende, with biotite and sphene as 

 accessories. The three principal constituents occur for the most 

 part as allotriomorphic grains. Now and then the quartz appears- 

 to form inclusions in the felspar and hornblende. The micro- 

 structure is granitic, not granulitic. Mr. Teall adds that there 

 is no doubt a close resemblance between this rock and basic portions 

 of the Lewisian Gneiss occurring between Laxford and Cape 

 Wrath. 



The granular gneiss (group 3), which extends from Armadale 

 Bay westward for a distance of | mile, is a rather fine-grained 

 granular rock, containing quartz, felspar (including oligoclase),, 

 biotite, and sometimes hornblende. This group is associated with 

 highly quartzose schists or gneiss, with magnetite in well-formed 

 octahedra. 



The Cipolin group (no. 5) is in some respects the most interesting 

 of this series. The rocks included in this group are exposed in a 

 burn draining into the sea, about -| mile W.N.W. of the village- 

 of Armadale. In the lower part of its course, where it flows 

 through a rocky gorge, a band of crystalline limestone is exposed at 

 the base of the cliff. One specimen from this locality has been 

 named by Mr. Teall a banded cipolin, one band being mainly com- 

 posed of crystalline calcite. Under the microscope it shows scapolite, 

 calcite, quartz, a pale green pyroxene, and sphene. Scapolite is the 

 most abundant mineral in that portion of the rock from which tho 



