112 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 1 894, 



as that where the inclusions are said to be found. At this place he 

 had on a former occasion described the occurrence of numerous veins 

 proceeding from the mass of granite there and traversing the gabbro, 

 and if these observations were correct they afforded a complete 

 demonstration that Prof. Judd had reversed the order of appearance 

 of the two rocks ; moreover, he considered that his own view of the 

 case received corroboration at many other localities in the Western 

 Isles. "With reference to the case mentioned by Sir A. Geikie in 

 the Cuillin Hills, Prof. Judd alleged that earlier writers had failed 

 to discover any veins proceeding from the granite into the gabbro, 

 whilst he had himself searched for such evidence without being able 

 to find anything of the kind. It is fortunate that we are not on the 

 present occasion called upon to decide on the merits of this case, 

 which, in its narrower issues, resolves itself very much into a 

 matter of field-geology. The general question as to whether the 

 great acid eruptions of the Hebrides preceded or succeeded the basic 

 ones is probably too large to be decided by the evidence of a single 

 locality. Indeed, when we have to deal, not with one, but with a 

 multiplicity of volcanic complexes, it is just possible that one section 

 may tell a story which another section contradicts. 



Once more the venue shifts to the North-west Highlands — to the 

 mainland of Sutherland and Eoss — and we are again led to consult 

 Messrs. Peach and Home as to the igneous rocks in the Torridon and 

 Cambrian formations. These occur as intrusive masses on several 

 horizons. The famous Loch Borolan porphyry finds a place here, 

 and this rock may be further studied in a recent contribution to the 

 Transactions of the Royal Society of Edinburgh 1 by Messrs. Home 

 and Teall, where those authors describe ' Borolanite ' as an igneous 

 rock intrusive in the Cambrian Limestone of Assynt and the Torridon 

 Sandstone of "Western Ross. The proofs of the intrusive nature of 

 these masses are said to be conclusive, more especially in the alter- 

 ation produced by them in the Ledbeg marbles. They have been 

 injected along the bedding-planes, and in some cases so regularly 

 that it was at one time thought they were contemporaneous lava- 

 flows. On the western face of Canisp a mass of porphyritic felsite 

 rises from the old platform of Archaean gneiss, passing upwards into 

 the overlying Torridon Sandstone and eventually spreading along 

 the bedding-planes. Detailed mapping indicates the positions 

 occupied by these igneous masses throughout the Torridon and 

 Cambrian beds. It is considered that the outbreak of plutonic 



1 Vol. xxxvii. (1691 ) part i. p. 163. 



