GEOLOGY OF THE OUTER HEBRIDES. 563 



it to be an exceedingly rough deposit of boulders and 

 smaller blocks imbedded in a coarse, compacted gravel, and 

 all deeply coloured reddish-brown by a staining of iron- 

 peroxide. This external appearance naturally suggests 

 that this Conglomerate is identical with the Red Sandstones 

 and Conglomerates on the opposite side of the Minch. A 

 careful examination, however, shows that the component 

 blocks, pebbles and cementing matrix are but fragments, 

 great and small, from the adjacent crystalline and schistose 

 rocks, in situ. Blocks of gneiss of all sizes up to three feet, 

 variously coloured : grey, dark, and orange as the pre- 

 dominance of felspar or hornblende shows in the block, are 

 imbedded in large numbers throughout the deposit. Blocks 

 are to be seen at Aignish at high-water mark at the foot 

 of cliffs of a loosely coherent sandstone and of a deep 

 chocolate-brown. No other blocks are seen in or near this 

 mass of sandstone. These blocks ring to the hammer, but 

 when broken show an intensely compacted agglomerate of 

 the same ingredients as the general mass of the Conglome- 

 rate. Associated with the fragments of gneiss are granules 

 of calcite and a greenish mineral pronounced to be pinite, 

 and rare. The calcite is coarsely granular, and largely 

 prevails in the Conglomerate, as may be seen by testing 

 any chance fragment of it by hydrochloric acid. The 

 calcite fills crevices, forms the cementing matrix largely, 

 and appears in horizontal bands along the faces of the cliffs. 

 The beach at Holm is strewn with gneissic pebbles washed 

 out of the cliffs. These pebbles are composed of quartz, 

 hornblende, and that melange of epidote with quartz and 

 felspar to which Heddle has given the name " Epidosite." 

 The cliffs in this district are full of these peculiar pebbles 

 and blocks. Besides these prevailing rocks and minerals, 

 there are to be found bits of greenish, argillaceous schists 

 fastened in the calcite matrix of some fragments. At Coll, 

 on the north of Broad Bay, there are blocks of gneiss in the 

 cliffs in which mica is found, in addition to the ordinary 

 constituents, quartz, felspar, and hornblende. The large 

 amount of haematite flakes, or scales rather, closely resem- 



