320 GRANOPHntEs of strath (skye). [May 1896. 



18. On certain Granophyres, modified by the Incorporation of 

 Gabbro-Fragments, in Strath (Skye). By Alfred Harker, 

 Esq., M.A., F.G.S., Fellow of St. John's College, Cambridge. 

 (Communicated by permission of the Director-General of the 

 Geological Survey. Head February 26th, 1896.) 



[Plates XIII. & XIV.] 



The district of Strath in Skye, which has so often formed the 

 subject of geological description, has been assigned to me to be 

 mapped in detail for the Geological Survey ; and while engaged in 

 this duty, during the past summer and a portion of the autumn, I 

 had occasion to study the complex series of eruptive rocks which 

 extends from Loch Slapin on the west to the Sound of Scalpay and 

 Broadford Bay on the east. Among the features of interest con- 

 nected with these igneous rocks, special importance attaches to 

 their relations one to another, and this subject has received due 

 attention. The full details will be fitly deferred until the appear- 

 ance of the official Memoirs ; but, with the sanction of the 

 Director-General, I now present to the Society the following brief 

 account of certain minor intrusions of granophyre illustrating a 

 peculiarity which, I believe, has not yet received notice. 



The granophyres of Skye have been described, as a whole, by 

 Macculloch, Oeynhausen and von Dechen, J. D. Forbes, Sir Archi- 

 bald Geikie, 1 Prof. Zirkel, and Prof. Judd. Despite mineralogical 

 and textural variations, these rocks have a general community of 

 characters, which they share also with rocks of various ages in 

 other regions. The examples to be described, however, present 

 quite exceptional features, which seem to be worthy of examination. 

 They form five distinct intrusions lying north and west of Loch 

 Kilchrist and 2 or 3 miles south-west of Broadford (see Map). 

 At this locality occurs a large tract of massive volcanic agglomerate, 

 which has its own interest as marking, according to Sir A. Geikie, 2 

 the site of a large volcanic vent. It is within, and on the borders 

 of, this agglomerate- tract that the intrusions are situated. In the 

 surrounding district numerous other masses of granophyre occur. 

 Immediately to the north is the large boss forming the Bed Hills ; 

 to the south is another rising into Beinn-an-Dubhaich, while 

 several smaller intrusions are perhaps to be regarded as offshoots 

 from these large ones ; but from all of these the peculiar rocks in 

 question are at once picked out in the field as presenting marked 

 differences from them. 



1 I follow Sir A. Geikie in grouping all the Tertiary acid rocks of this region 

 under the collective name ' granophyre,' which is strictly applicable to most of 

 them, although there are transitions both to the granitoid type on the one hand 

 and to fine-textured ' quartz-felsites ' on the other. 



2 Trans. Eoy. Soc. Edinb. vol. xxxv. (1888) pp. 107-109. 



