in Torridonian Conglomerates. 449 



On several occasions I have found pebbles in the Torridon Sand- 

 stone which appeared indistinguishable from the Moine rocks; and 

 I recently collected several from a locality which affords an especially 

 useful test. They were obtained on the northern shore of Little 

 Loch Broom, a quarter of a mile west of Badralloch, from cliffs of the 

 Applecross or middle division of the Torridon Sandstone. The 

 conglomerates there contain many pebbles which exactly resemble 

 the typical rocks of the Moine Series. Dr. Teall has kindly examined 

 five of the specimens and slides cut from them ; and he writes, " the 

 three rocks (M 1, M 2, and M 5) are undoubtedly of Moine type, and 

 the two quartzose rocks (M 3 and M 4) are like rocks associated with 

 granulitic gneisses of the Moine group. I believe that all five rocks 

 could be matched by rocks from areas mapped as Moine." The 

 specimens have also been examined by Dr. Home, who says, "there 

 can be no doubt that they are typical siliceous granulites of Moine 

 type." Mr. Tyrrell independently examined the slides, and he also 

 says that three of the five specimens are typical granulitic Moine 

 rocks ; the other two, he remarks, are quartzites without distinctive 

 features. 



Dr. Home remarked that it is possible such rocks might occur 

 among the altered sediments of the Loch Maree type which are 

 referred to the Lewisian. 1 This possibility seems remote. The 

 nearest exposure of the Lewisian rocks is about 2\ miles from 

 Badralloch on the opposite side of Little Loch Broom, and in that 

 district they are the normal type ; and the altered sediments which 

 are referred to the Lewisian are 15 miles to the south. The Moine 

 rocks of Loch Broom are well exposed about five miles from 

 Badralloch, though this proximity may be due in part to the 

 overthrusting. The Moine rocks nearest Badralloch include both 

 the granulitic micaceous gneiss and granulitic quartzite which occur 

 as pebbles in the Torridon conglomerates. The quartzitic type has 

 been described by Gunn (Geol. Surv. Memoir, 1907, p. 611), who 

 says that in this district " there are also highly siliceous and 

 massive kinds which approach the nature of quartzite, and contain 

 little mica of any kind". These rocks are well exposed on the road 

 south-east of Ullapool, near the head of Loch Broom. 



The Torridonian pebbles of Little Loch Broom therefore differ 

 from the local Lewisian rocks and are indistinguishable from the two 

 typical rocks of the nearest outcrop of the Moine Series. Hence it 

 appears more reasonable to regard these pebbles as derived from the 

 similar local Moine rocks than to refer them to a hypothetical 

 Lewisian source three times as far distant. 



It maybe urged that the presence of Moine pebbles in the Torridon 

 Sandstone does not prove that all the Moine is pre-Torridonian ; for 

 the Moine may consist of two elements — (1) pre-Torridonian Moine 

 rocks, from which these pebbles have been derived ; and (2) Torridon 

 Sandstone which has been altered into such Moine-like granulitic 

 gneisses that they have been mapped by the Geological Survey as 



1 The Fannich memoir, Sheet 92, 1913, p. 9, remarks, however, that the 

 relations of these altered sediments " to the members of the Fundamental 

 Complex have not been definitely determined ". 



DECADE VI. — VOL. II.— NO. X. 29 



