634 KEFOET— 1891. 



determinalile fossils associated wath tliem in the same primeval restino--place. We 

 shall spare no pains to bring to light all that can be recovered in the North-west 

 Highlands of a pre-Cambrian fauna. 



2. On some recent Work of the Geological Survey in the Archcean Gneiss 

 of the North-west Highlands. By Sir Archibald Geikie, F.B.8., 

 Director-General of the Survey. 



For some years past the officers of the Geological Survey have spent much 

 time and labour upon the investigation of the old or fundam'ental gneiss of the 

 North-west Highlands. They have succeeded in showing that it consists mainly 

 of materials which were originally of the nature of eruptive igneous rocks, but 

 which by a long succession of processes have acquired the complicated structures 

 which they now present. No evidence of anything but such eruptive rocks had 

 been met with until the mapping was carried into the west of Ross-shire. In that 

 area it had long been known that the gneiss includes some mica-schists and 

 limestones which were believed to be integral parts of its mass. With the 

 accumulated experience of their work further north my colleagues were naturally 

 predisposed to accept this view, and to look on even the limestones ae the result 

 of some crushing-down and re-formation of basic igneous rocks containing lime 

 silicates ; but as they proceeded in their work they encountered various difficulties 

 in the acceptation of such a theoretical e.xplauation. lu particular they found 

 that with the mica-schist were associated quartz-schists and graphitic schists, and 

 that the limestone occurred iu thick and persistent bands, with included minerals 

 like those found in the Eastern Highlands in districts of contact metamorphism. 

 The microscopic examination of some of these rocks showed them to present 

 close affinities to certain members of the crystalline series of the Eastern and 

 Central Highlands, which can be recognised as consisting mainly of altered sedi- 

 mentary strata (Dalradian series) ; j-et the officers of the Survey could not 

 separate these doubtful rocks from the surrounding gneiss. The several materials 

 seemed to pass in.sensibly into each other in numerous sections, which were 

 examined with great care. Within the presc'nt month, however, one of the 

 members of the staff, Mr. 0. T. Clough, who has been specially engaged in this 

 investigation, baa obtained what may prove to be conclusive evidence on 

 the subject. He has ascertained that the main bands of graphitic schist occur 

 evenly bedded in an acid mica-schist, in which also these graphitic layers are 

 distributed at intervals of an inch or less. These rocks are sharply marked ofi 

 from the true gneiss, though where they actually join they appear to be, as it 

 were, crushed along a line of intense movement. Mr. Clough and his colleagues 

 are at present disposed to believe that these schists are really an older series of 

 sediments, into which the original igneous rocks now forming the gneiss were 

 erupted. If they succeed in demonstrating the correctness of this inference they 

 will have established a fact of the greatest interest in regard to the geological 

 history of our oldest rocks. Already they have shown the thick masses of 

 Torridon sandstone to be an accumulation of sedimentary materials of pre- 

 Cambrian age. They will push back the geological record to a still more remote 

 past if they can establish the existence of a yet more ancient group of sedi- 

 mentary strata, among which layers of graphite and beds of limestone remain to 

 suggest the existence of plant and animal life. 



3. Beport of the Committee on the Registration of Type Specimens. 

 See Reports, p. 299. 



4. BemarJce on the Lower Tertiary Fish Fauna of SarJi^iia. 

 By A. Smith Woodward, F.G.S. 

 The author referred to a series of fragmentary fish-remains from the Miocene 

 of the neighbourhood of Cagliari, Sardinia, collected and submitted for exami- 



