determinable fossils associated with them in the same primeval resting-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 Archæan Gneiss of the North-west Highlands. By Sir ARCHIBALD GEIKIE, F.R.S., 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 fundamental 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 as 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 explanation. In particular they found that with the mica-schist were associated quartz-schists and graphitic schists, and that the limestone occurred in 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 sedimentary strata (Dalradian series); yet the officers of the Survey could not separate these doubtful rocks from the surrounding gneiss. The several materials seemed to pass insensibly into each other in numerous sections, which were examined with great care. Within the present month, however, one of the members of the staff, Mr. C. T. Clough, who has been specially engaged in this investigation, has 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 off 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 preCambrian 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 sedimentary strata, among which layers of graphite and beds of limestone remain to suggest the existence of plant and animal life. 3. Report of the Committee on the Registration of Type Specimens. See Reports, p. 299. 4. Remarks on the Lower Tertiary Fish Fauna of Sardinia. The author referred to a series of fragmentary fish-remains from the Miocene of the neighbourhood of Cagliari, Sardinia, collected and submitted for exami nation by Professor D. Lovisato. A memoir on the subject by Professor F. Bassani had lately appeared ('Atti R. Accad. Sci. Napoli, Series 2, vol. iv., Mem. No. 3, 1891), and the present communication contained only brief supplementary observations. In addition to the Selachian genera and species recognised by Bassani, the author identified teeth of Scymnus, Oxyrhina Desori, Galeus, Aprionodon, and probably Physodon, besides dermal scutes of Trygon. The collection comprises no evidence of ganoid fishes, and most of the remains of teleosteans are too imperfect even for generic determination. Traces of Scomberoids and Labroids occur, and there is evidence of a new species of the Berycoid Holocentrum. Teeth of Chrysophrys, Sargus, and other common Mediterranean genera are abundant; and a few detached yellow teeth represent an indeterminable species of Balistes. 5. Evidence of the Occurrence of Pterosaurian and Plesiosaurian Reptiles in the Cretaceous Strata of Brazil. By A. SMITH WOODWARD, F.G.S. The author exhibited and described two examples of the articular end of the quadrate bone of a Pterodactyl, and one imperfect propodial bone of a Plesiosaur, discovered by Mr. Joseph Mawson, F.G.S., in the Cretaceous Formation near Bahia, Brazil. Though not generically determinable, the fossils are of much interest as being the first evidence of the reptilian orders in question from the Mesozoic deposits of South America. 6. The Cause of Monoclinal Flexure. By A. J. JUKES-BROWNE, F.G.S. Folds of the ordinary arch and trough type are generally ascribed to the influence of lateral pressure; but it is not easy to see how a monoclinal flexure which appears in section as a flexure connecting two horizontal bars of strata can have been produced by direct lateral pressure exerted at the ends of the bars. The author suggests that monoclinal flexuring is a structure impressed upon a horizontal series of uncompressed strata by the displacement of a subjacent mass of faulted and flexured rocks, the lateral compression of the deep-seated mass resulting in the vertical uplift of certain portions of the 'cover.' If a series of stratified rocks rests in a horizontal position on a mass of ancient rock, which has been compressed, indurated, flexured, and faulted before the deposition of the upper series, it is supposed that the lower series of rocks would give way under lateral pressure along the pre-existing faults, and that the blocks which lie between upward diverging faults would be forced to move upwards, carrying with them those tracts of the 'cover' which rest on them. It is evident that these tracts would be divided from those resting on blocks defined by downward diverging faults by faults or monoclinal flexures, the production of a fracture or a flexure depending partly on the thickness and pliability of the strata forming the cover and partly on the amount of local uplift. It is conceivable that the displacement might take place partly by faulting and partly by flexuring, and that what was a fault near the plane of unconformity might pass upward into a flexure. The writer desires criticism on the above suggestion, especially from those who will have a chance of seeing the grand monoclinal flexures of the Colorado region during the excursion of the approaching International Geological Congress. 7. Note on an Undescribed Area of Lower Greensand, or Vectian, [Communicated by permission of the Director-General of the Geological Survey.] A recent examination of the ground below the escarpment of the Chalk in North Dorset has revealed the existence of a tract of Vectian or Lower Greensand which had not previously been suspected. Reference to the Geological Survey ' Published in extenso in Ann. Mag. Nat. Hist. [6] vol. viii. pp. 314-317. map, Sheet 15, will show that the Gault was supposed to thin out and disappear near Shaftesbury, so as to allow the Upper Greensand to rest directly on the Kimmeridge Clay. This proves to be a mistake; the Gault is continuous into and beyond the valley of the Stour. Moreover two miles south of Shaftesbury a tract of sand emerges from beneath the Gault, and forms a terrace which for a little distance has a separate escarpment of its own. Near Bedchester this tract of sand is nearly half a mile wide, and thence it can be traced to Child Okeford, on the eastern side of the Stour valley, its length being between four and five miles. Exposures near Bedchester show that it consists chiefly of quartz sand containing a variable amount of glauconite, some beds being yellow and consisting chiefly of quartz, others being grey or dark green and containing a large amount of glauconite. There is also a bed of greenish-black glauconitic clay, 24 feet thick, consisting of dark purple clay and minute grains of dark green glauconite intimately mixed together. Most of the sand is of fine grain, but there are some thin layers of coarse sand. So far as is yet known, and with the exception of a small exposure near Lulworth Cove, this is the most westerly tract of Lower Greensand in England. 8. On the Continuity of the Kellaways Beds over extended areas near Bedford, and on the Extension of the Fuller's Earth Works at Woburn. By A. C. G. CAMERON. [Communicated by permission of the Director-General of the Geological Survey.] In this paper further evidence is submitted from different parts of the country, of the continuity over extended areas of the Kellaways Rock above the Lower Oxford Clay. Several fine excavations, the result of railway enterprise, have afforded sections of these beds in places where their presence was only inferred before. More than the usual thickness is indicated by records recently obtained from deep sinkings and borings in the Midland districts, especially the Bletchley boring of 1886-7. The extraordinary concretionary stones, noticed in Wiltshire by Smith as characterising this formation, and quarried away years ago at Kellaways for roadstone, jut out in the Valley of the Churn, near Cirencester, and stand about in clusters in the Valley of the Ouse at Bedford like gigantic fungi. The plane of separation of the Upper Oxford and the Kellaways in Bedfordshire is formed by a shelly calcareous band in contact with a shelly cap to the concretionary stones. Where this plane is a broken one there is no development of concreted rock, and the lowest sediment of Upper Oxford clay is loamy, passing down into Kellaways sand. Above the calcareous band there is sometimes an indurated seam of sandy marl, breaking into conical forms; the product, apparently, of stalactitic infiltration. Pits are opened at the outcrop of the Kellaways (a persistent stratum in the Ouse Valley) and are carried down through the Lower Oxford (selenite clay), Cornbrash and Cornbrash clay to Great Oolite limestone, which is quarried for lime-burning; the 'lam earth,' the loamy portion of the Kellaways, being mixed in the mill with the Lower Oxford, which is dug for brickmaking. Excellent sections, showing the above series, are to be seen. Observations on the extension of the Fuller's Earth Works at Woburn Sands, with some description of the beds, are given, and the mining industry now springing up is commented on. FRIDAY, AUGUST 21. The following Papers were read: 1. On the Discovery of the South-Eastern Coal-field. The author pointed out that although the physical identity of the SouthWestern coal-fields with those of Northern France and Belgium was recognised by Buckland and Conybeare as far back as 1826, it was reserved for GodwinAusten to point out the possibility (in 1855) and the probability (in 1858) of the extension of the coal measures under the secondary rocks of South-Eastern. These views were ratified by Prestwich, before the Coal Commission in 1866. After referring to the sub-wealden boring, abandoned when carried to a depth of 1,904 feet, the author stated that in 1886 he recommended to Sir E. Watkin that a boring should be made on the site of the Channel Tunnel works, almost in sight of Čalais, where the coal measures had been reached at 1,104 feet, and near the spot where about four hundredweight of bituminous material, possibly derived from the coal measures below, had been found in the chalk. Professor Prestwich had pointed out in 1873 the possibility of tunnelling across the Channel in the older rocks, and Mr. Whitaker had also pointed out in 1886 the desirability of making trial for coal at Dover. A shaft was sunk on the west side of Shakespeare's Cliff to a depth of 44 feet, and from the bottom of this a bore-hole was carried to a depth of 1,500 feet, through the following strata: Cretaceous, 500 feet; Jurassic, 613 feet; Coal measures, 387 feet. The first seam of coal was struck at 1,140 feet, and five other seams were met with at intervals down to 1,500 feet, giving, according to Mr. Brady, 10 feet of workable coal in all. These coal measures dipped gently at an angle of 2 degrees to the south, and are clearly within the limits at which mining can be carried on at a profit, for the British coal-fields are worked to depths of 3,000 feet, those of Belgium to 4,000 feet, and year by year the improved means of ventilation carry the limit downwards. The coal is bright and blazing, with cleat slightly lozenge-shaped, and, although with marks of crushing in two seams, is much less injured in this respect than the coals of the Boulonnais. Comparison with the Westphalian coal-field, which has 294 feet of workable coal, that of Liège with 212 feet, that of Mons with 250 feet, and that of Somerset with 98 feet, suggests that the discovery of other and thicker seams is merely a question of sinking deeper. In conclusion, the author pointed out the importance of a new coal industry in the south-east of England, carrying in its train many other industries, and not improbably reviving under more favourable conditions the ancient wealden ironfield, while he also indicated the important bearing of these discoveries on the question of the durability of our coal supply. The Geology of Petroleum and Natural Gas. The object of this paper is to give a summary of some of the more important facts as to the geological conditions under which petroleum and natural gas are found in various parts of the world, noting the geological ages of the rocks in which they occur, and the influence of geological structure in determining this occurrence. Few cases are known in which petroleum occurs in rocks older than the Silurian, and none where the amount is of any importance.. Petroleum occurs, but not in large quantity, in a trachyte-breccia at Taranaki, New Zealand. In N.W. Hungary it is .found in a trachytic tuff of Miocene age, and in some other areas small indications of petroleum are found in volcanic rocks. These, however, are exceptional cases; for in the great majority of cases petroleum is far removed from any known indications of true volcanic action. The great stores of petroleum and gas in Pennsylvania and New York are in sandstone beds of the Devonian and Lower Carboniferous rocks. Of late years great quantities of gas and oil have been obtained, chiefly in Ohio and Indiana, from the Trenton Limestone (Ordovician). The oil and gas-fields of Pennsylvania and New York have a very simple geological structure. The rocks lie comparatively undisturbed, being only gently folded into a series of anticlinals and synclinals parallel with, and along the N.W. side of, the main axes of the Alleghanies. These folds have themselves a gentle inclination towards the S. W. In the Alleghanies, and to the S.E. of the range, where the rocks are greatly disturbed, neither oil nor gas is found. Some of the larger gas wells are on or near the summits of anticlinals, but many are not so placed. In the Trenton Limestone fields of Ohio and Indiana the productive areas are mainly over anticlinals, gas occurring at the crown of the arch, oil on the slopes. The essential conditions for a largely productive field of gas or oil are a porous reservoir (generally sandstone or limestone) in which the hydrocarbons can be stored, and an impervious cover of shale retaining them in the reservoir. It is also believed that they only occur where, in or under the porous reservoir, there have been accumulations of fossil remains, the original decomposition of which yielded the hydrocarbons. In the case of the sandstones the original source was probably the fossiliferous shales which underlie them; in the case of the Trenton Limestone the source was probably the fossiliferous limestone itself. The limestone is only productive under certain circumstances; in its normal condition it is a compact rock, and then it contains neither gas nor oil. But over large areas the limestone has been dolomitized, and so transformed into a cavernous and porous rock in which gas and oil are stored. The enormous quantities of gas and oil given out from beds of limestone and sandstone can be fully accounted for when their porous nature, thickness, and extent are taken into consideration. Some of these rocks can contain from th to 4th of their bulk of oil. The high pressure under which gas and oil flow from deep borings can in most cases be fully explained by artesian pressure. In Kansas gas occurs mainly in the Lower Coal Measures. In Kentucky and Tennessee oil is found in the Ohio shales (Up. Devonian), in Colorado in shales of Cretaceous age. In California it is found in Tertiary strata, mostly much disturbed. In Canada the chief source, in Ontario, is in Devonian rocks, along a wellmarked anticlinal; but gas and oil also occur in the Trenton Limestone. In the North-West Territories there seem to be great stores of oil in Devonian rocks. Gas and oil now found in Cretaceous strata of the prairies and Athabasca may have been derived from underlying Devonian rocks; but in the Rocky Mountains, at Crow's Nest Pass, oil is probably native to the Cretaceous beds. In Mexico, the West Indies, and parts of South America, Tertiary strata seem to be the chief source of oil. The age of the petroleum-bearing unfossiliferous sands, &c., of the Argentine Republic (province of Jujuy) is not certainly known; they have been referred by different writers to various ages from Silurian to Tertiary; they are probably sub-Cretaceous. In Europe and Asia the petroleumbearing beds are of Secondary or Tertiary age, the Paleozoic rocks yielding only an insignificant supply. In North-west Germany we find petroleum in the Keuper Beds, and more or less in other strata up to and including the Gault. As we pass to the south and south-east from this district we find, as a general rule, that oil occurs in newer strata. The various productive horizons of different districts are as follows: |