October 3, 1901] 



NA TURE 



565 



Fragments of Rhcetic, Liassic and Cretaceous rocks which must 

 once have covered the area have been recognised by their fossils 

 in a large volcanic vent ; this volcano was probably of Tertiary 

 age, to which period are also assigned most of the igneous 

 rocks, though six earlier periods of volcanic activity have been 

 now recognised in this most interesting island. 



Mr. G. Barrow followed with a suggestive paper on lateral 

 variations of composition in zones of the Eastern Highland 

 schists, which he ascribed to original variation in the sediments 

 deposited in a delta. Mr. P. Macnair then gave his inter- 

 pretation of the structure and probable succession of the schists 

 of the Southern Highlands, which he considers to form an 

 ascending sequence in the following order : Lower Argillaceous 

 zone. Lower Arenaceous zone, Loch Tay Limestone, Garneti- 

 ferous schist. Upper Argillaceous zone and Upper Arenaceous 

 zone. 



The difTerentation of a rock-magma was well illustrated by 

 Prof. J. Geikie and Dr. J. S. Flett in their description of the 

 granite of Tulloch Burn, Ayrshire, which passes at its margins 

 into intermediate and basic rocks. 



The occurrence of a phosphatic layer at the base of the 

 Inferior Oolite in Skye, lining a hollow of local erosion in the 

 Upper Lias shales, was briefly described in a paper by Mr. H. B. 

 Woodward. 



On Friday the first paper was a lucid account by Sir Arch. 

 Geikie of the re-discovery of a tree-trunk embedded in volcanic 

 ash in Mull. This tree was described long ago by Macculloch, 

 but occurs in a sea-cliff very difficult of access, and received no 

 further notice until visited recently by Sir .\rch. Geikie. The 

 stump is about 5 feet in diameter and 5 feet high, and must have 

 belonged to a tree originally at least So feet high. It is of 

 peculiar interest in showing that time-intervals of quiescence 

 of considerable length occurred between separate volcanic 

 outbursts. 



Another notable contribution to Scottish volcanic geology was 

 made by Mr. A. Harker in a paper on the sequence of the 

 Tertiary igneous eruptions in Skye, read by Dr. Flett in the 

 absence of the author. As the result of his detailed mapping 

 of the volcanic rocks of Skye for the Geological Survey, Mr. 

 Harker finds that he can recognise three successive phases of 

 igneous activity — the volcanic, the plutonic, and the phase of 

 minor intrusions. He further distinguishes two parallel series 

 of events — the regional and the local, the former of very wide 

 extension, the latter connected with certain definite foci, one of 

 which was situated in Central Skye. 



The regional eruptive rocks are all of basic composition, but 

 the local groups exhibit much greater diversity. During the 

 plutonic phase the successive groups of intrusions at the Skye 

 centre followed an order of increasing acidity ; but for the local 

 groups of the succeeding phase of minor intrusions this order 

 was reversed. Mr. Harker suggests that this sequence of 

 Tertiary igneous eruptions may probably be taken as a type of 

 the whole British area ; and we may be sure that all students 

 of these difficult rocks will await with impatience the publication 

 of the detailed observations on which Mr. Harker's far-reaching 

 generalisations are based. 



Two papers by Messrs. A. McHenry and J. R- Kilroe, of the 

 Irish branch of the Geological Survey, dealing with the older 

 rocks of the north-west of Ireland and their bearing on .Scottish 

 geology, were next read. In the first the authors called atten- 

 tion to the close resemblance of the Old Red Sandstone of north- 

 west Ireland to the Torridon rocks of Sutherland both in 

 composition and structural relationships, and suggested that the 

 Torridon rocks were therefore really of Old Red age. Tnis 

 paper gave rise to an animated discussion, in which Profs. Sollas, 

 Lapworth and Hull, Messrs. Peach, Barrow, Greenly, Good- 

 child, Caddell, Hinxman, Craig and the President took part. 

 The consensus of opinion was that the suggested new reading of 

 the Torridon succession could not be sustained ; and one of the 

 speakers aptly proposed that as the question had been well- 

 threshed out, an abstract of the discussion should be printed as a 

 permanent record of the evidence for the age of the Scottish 

 Torridonian. 



Messrs. Kilroe and McHenry's second paper dealt with the 

 relation of the Silurian and Ordovician rocks of north-west 

 Ireland to the Great Metamorphic Series, their contention being 

 that the latter consisted of metamorphosed Lower Silurian 

 sediments and associated intrusions, over which the unmeta- 

 morphosed rocks were carried by overfolding and great disloca- 

 ons in Llandovery times. In the next paper on the list, by 



Mr. G. H. Kinahan, this view was controverted, and the earlier 

 age of the metamorphic series upheld, these being compared 

 with the .A.lgonkian of North America. 



Dr. Traquair then gave interesting lantern demonstrations on 

 the geological di.stribution of the fishes of the Carboniferous 

 rocks and of the Old Red Sandstone of Scotland. The study of 

 the Carboniferous fish-faunas led to the conclusion that the rocks 

 were divisible into two parts— Upper and Lower Carboniferous, 

 with a great break at the base of the Millstone Grit, the Upper 

 Carboniferous fauna being like that of England, and that of the 

 Lower Carboniferous differing only where fresh-water or 

 estuarine conditions displaced the marine forms. At a later 

 session similar results were presented by Mr. R. Kidston in his 

 description of fossil plants from Berwickshire. 



In the concluding papers on Friday the Section was carried 

 far afield by Miss C. A. Raisin in her account of the volcanic 

 rocks of Perim Island, and by Dr. R. Logan Jack in his 

 description of the conditions under which enormous supplies of 

 artesian water are obtained in 'Queensland, where borings of 

 the aggregate length of 1S5 miles have been made with incal- 

 culable advantage to the country, as the result of geological in- 

 vestigations in which Dr. Jack was a pioneer. The deepest of 

 these borings attained the exceptional depth of 5045 feet. 



On Monday, when precedence was given to palfeontological 

 papers, Mr. B. N. Peach came first with an admirable rt'sumJ of 

 our knowledge of the Cambrian fossils of the North-West High- 

 lands, in which stress was laid on the close agreement between 

 the Scottish and North American fossil zones of this ancient 

 period, betokening a shore-line connection between the con- 

 tinents, with a deep-water barrier to the southward, separating 

 the north of Scotland from the mid-European and Welsh areas. 

 Prof. Sollas then exhibited and explained his machine for 

 investigating fossil-remains. By Prof. Sollas's method the fossil 

 is ground down slowly, and a series of parallel sections obtained 

 from which it is easy to construct a model of the whole fossil. 

 The great value of this machine as an instrument of research 

 was demonstrated by a series of lantern slides and by wax 

 models. 



Mr. A. M. Bell gave an account of the plants and coleoptera 

 from a Pleistocene deposit at Wolvercote, Oxfordshire; the 

 plants indicated a more continental climate of the Thames 

 valley during the period than at present, and a later date for the 

 deposit than the Hoxne beds. 



Papers on glacial geology were fewer than of late years, and 

 indeed, with the e.xception of the Report of the Erratic Blocks 

 Committee, the only strictly glacial paper was that of Prof. 

 P. F. Kendall and H. B. Muff' on overflow channels and other 

 phenomena indicating glacier-dammed lakes in the Cheviots, in 

 which region these observers have recently recognised similar 

 phenomena to those which they had previously investigated in 

 Yorkshire. 



The application of geology to agriculture by the preparation 

 of soil maps was the subject of a communication by Mr. T. R. 

 Kilroe, who exhibited a specimen-map, on which the general 

 character of the soil was indicated by a few colours selected 

 from those of our usual geological maps, but intended to show 

 the soil-characters only, without particular reference to the geo- 

 logical structure. 



Tuesday was primarily the mineralogists' day, and the session 

 was opened by Mr. J. G. Goodchild with a paper on the 

 Scottish ores of copper in their geological relations, in which 

 these ores were classed into two primary categories, those of the 

 first being assigned to the uprise of thermal waters, and of the 

 second to solutions passing downwards from higher to lower 

 levels. The same author, in another communication, dealt 

 with a revised list of Scottish minerals, and indicated its 

 more salient points. Dr. W. Mackie followed with a series of 

 three papers on the Trias of Elgin and Nairn, one describing 

 the occurrence of barium sulphate and calcium fluoride as 

 cementing substances in the Elgin area, believed by the author 

 to have been directly depositeil during the concentration of the 

 waters of an inland lake ; another recording covellite and mala- 

 chite in a vein in the sandstone of Kingsteps, Nairn ; and the 

 third, on which there was an excellent discussion, on the pebble- 

 band of the Elgin Trias, which was shown to be of wider 

 extent than hitherto supposed and to mark a definite horizon 

 at the base of the Trias, the overlying Cutties Hillock sand- 

 stones being really made up of Triassic sand-dunes, while in 

 the pebble-bed many of the stones present characters showing 

 them to have been wind-worn. At this point we may also 



