[Footnote 229: On this subject consult Duke of Argyll, _Quart. Journ. Geol. Soc._ vol. vii. (1851), p. 89; E. Forbes, _Ibid._ p. 103; W. H. Baily, _op. cit._ xxv. (1869), pp. 162, 357; _Brit. Assoc. Rep._ (1879) p. 162; (1880) p. 107; (1881) p. 151; (1884) p. 209; Mr. J. Starkie Gardner, _Palæontographical Society_, vols. xxxviii. xxxix. In the last of Mr. Baily's papers he notices that "the Rev. Dr. Grainger found a portion of a fish (_Percidæ_, possibly _Lates_)." The discovery of the remains of a fresh-water fish is an important additional testimony to the terrestrial conditions under which the lavas were erupted. The genus _Lates_ now inhabits the Nile and the Ganges.] For the purpose of the present volume, however, the precise stage in the geological record, which this flora indicates, is of less consequence than the broad fact that the plants prove beyond all question that the basalts among which they lie were erupted on land during the older part of the long succession of Tertiary periods. Their value in this respect cannot be overestimated. Stratigraphical evidence shows that the eruptions must be later than the Upper Chalk; but the imbedded plants definitely limit them to the earlier half of Tertiary time. CHAPTER XXXVII THE SEVERAL BASALT-PLATEAUX AND THEIR GEOLOGICAL HISTORY, ANTRIM, MULL, MORVEN AND ARDNAMURCHAN There are five districts in North-western Europe where the original widespread Tertiary lava-fields have been less extensively eroded than elsewhere, or at least where they have survived in larger and thicker masses. Whether or not each of them was an isolated area of volcanic activity cannot now be determined. Their several outflows of lava within the area of the British Isles may have united into one continuous volcanic tract, and their present isolation there may be due entirely to subterranean movements and denudation. There is a certain convenience, however, in treating the districts separately. They are--1. Antrim; 2. Mull, Morven and Ardnamurchan; 3. Small Isles; 4. Skye; 5. The Faroe Islands. i. ANTRIM[230] [Footnote 230: The basalts of Antrim are the subject of an abundant literature. I may refer particularly to the papers of Berger and Conybeare (_Trans. Geol. Soc._ iii.), the Geological Report of Portlock, and the Explanations of the Sheets of the Geological Survey of Ireland. Other papers will be afterwards cited. The general features of the Antrim plateau are shown on Map VII.]