Geological Series Research Articles

On the Physical Structure of West Somerset and North Devon, and on the Palæontological Value of the Devonian Fossils

I. I ntroduction I t seems almost superfluous that another paper should be written upon the structure and succession of the Rocks of “West Somerset and North Devon;” but of late their position or place in the geological series has been questioned in an able paper by Professor Jukes*, in which he endeavoured to prove that the entire series of slates, sandstones, and limestones of the North Devon and West Somerset area belong partly to the Old Red Sandstone and partly to the Carboniferous rocks, rather than to the so-called Devonian Group, to which they have hitherto been considered to belong. In other words, Professor Jukes has propounded views as to the relative succession and physical structure of North Devon diametrically opposed to those held by most geologists, and based upon the investigations of Sir Roderick Murchison and Professor Sedgwick, Professor John Phillips, De La Beche, Weaver, and others; and he distinctly states that they have “all misunderstood the structure of the country,” and this arising chiefly from their having been previously unacquainted with the structure and succession of the lower members of the Carboniferous group of rocks, and with the upper series of the Old Red Sandstone, as shown in the South of Ireland ( the Irish Old Red Sandstone ). Professor Jukes also disputes the reality of the “time” succession (not the apparent) of the rock-groups of North Devon, i. e. those grits, slates, and sandstones which occur (in the Lynton area) from Lynton or the Foreland, on the north, to the

II. On the Classification of the Cretaceous Beds

The two Memoirs by Dr. Reynès, on the Cretaceous formation, which were noticed in the ninth number of the Geological Magazine, suggest two questions: how far subdivisions there proposed are applicable to the Cretaceous series of this country; and, next, as to the sufficiency of the ground on which the synchronism of the subdivisions of geological formations has been based. The subject of the second Memoir, ‘De l'Étage,’ involves considerations which might be well extended to the whole range of the geological series: indeed, it will hardly be profitable to make much progress with the past physical history of the earth until rules for determining geological horizons shall be established.

Geology of the Isle of Man

While almost every week increases our knowledge of the geology of distant parts of the earth, there is one small island in the British seas, famed for its picturesque beauty, and peculiarly interesting on account of its historical associations, of the geological features of which very little is known, and even that little scarcely ever referred to in geological treatises. This may have arisen mainly from the fact of there having been as yet no official survey of this island; while those portions of the geological series represented in the Manx rocks having been typically established from other localities, it did not seem to present geological features sufficiently novel or peculiar to require any special investigation. Still, in the earlier years of the science, several eminent geologists did describe, with greater or less minuteness, some of its geological appearances: for example, Professor E. Forbes, who wrote a short account of Manx geology for one of the local guide-books; and a much more elaborate account was written by the Rev. J. G. Cumming, F.G.S., and published in 1848; but the rapid progress of the science, while it does not deprive these descriptions of all value, has in a great measure superseded them, and opened here a wide and almost untrodden field for the modern geologist. Having for several years resided on the island, and being convinced that many of the phenomena presented by the Manx rocks, if not altogether new to the geologist, are yet of remarkable interest, and capable of taking a great part in the solution of many of the problems which geologists are now endeavouring to solve, I have written the following brief account, with the view of diffusing, through the pages of the ‘Geologist,’ a more general knowledge of the geology of the Isle of Man, and in the hope of attracting to the subject that attention which it deserves.

Mr. Gregory's Elementary Geological Series and Collections.

Mr. Gregory's Elementary Geological Series and Collections.

On the Old Red Sandstone Rocks of Forfarshire

The stratified rocks of Forfarshire, to the south of the Grampian range, belong entirely to the Old Bed Sandstone division of the geological series. They consist chiefly of coarse grits, dark-red and grey sandstones and flagstones, immense masses of conglomerate, with intercalated flagstones, sandstones, and shales, marly and argillaceous shales, and some crystalline limestones or cornstones. These, although in many instances broken up, and often faulted and contorted by trappean outbursts, all rest conformably the one upon the other. Thrown up against the flanks of the Grampian range at very high angles, and dipping towards the south-east, some very-fine sections are afforded by the streams which, issuing from these mountains, cut through the sandstones, in many instances in a line almost at right angles to their strike. Of these the North Esk, the West Water, the Koran, and the Isla may be mentioned as affording peculiar facilities for studying these formations. In all places I have yet examined the Forfarshire sandstones are cut off from the schists and slaty beds of the Grampians by considerable outbursts of trap; it is, however, pretty evident that the sandstones overlie these schists unconformably. Although I do not intend at present to go at all into the geology of the Highland districts of Forfarshire, I may here state that it seems to me highly probable that these schistose beds may be the equivalents of some portion of the Lower Silurians.

On some Fossiliferous Beds in the Silurian Rocks of Wigtownshire and Ayrshire

The difficulty of assigning to the great chain of rocks of the south of Scotland their true place in the geological series, arises from the rarity of fossil remains, and from the want of beds with such well-marked mineral character, as to enable the observer to determine their superposition. Part of this obscurity has been lately removed by Mr. Nicol's description of fossiliferous beds in the valley of the Tweed (Geol. Journ. vol. iv. p. 195); and as any additional information, however scanty, may be interesting, I shall briefly describe the localities in Wigtownshire and the south of Ayrshire where I have found fossils, commencing with some account of the general structure of the country. The description given by Mr. Nicol of the physical structure of Peeblesshire applies in the main to Wigtownshire and the south of Ayrshire. There is the same prevalent strike in an E.N.E. direction, a system of valleys running parallel to the strike formed by the convolutions of the rocks, with another transverse system of valleys at right angles to the former, remarkably equidistant, and through which the principal drainage of the country is effected. The rivers Stincher and Finnart are instances of the former system; the Cree, the Bladenoch and the Tarf, the Luce, and the Piltanton of the latter.

XVIII. Abstract of a Paper accompanying a Suite of Volcanic Rocks from the Lipari Islands, presented to the Royal Society

Having frequently had the pleasure of examining the very interesting and highly valuable collection of volcanic specimens brought from Iceland, and presented to the Royal Society by Sir George Mackenzie, I was gratified in an opportunity which was afforded me, at the close of 1830, of visiting the Lipari Islands, the only other great repository of obsidian in Europe, and of there collecting the suite of specimens which I have now the honour of presenting to the society. Unfortunately, it is far from complete as a geological series; for the difficulties occasioned by the tempestuous state of the weather, and the impossibility of getting to the more remote islands in a small boat during the month of December, limited my movements extremely, and forced me to confine my observations to the two principal islands of the group, viz. Lipari and Vulcano. I do not therefore pretend to give any geological account of these islands, or even of the two on which I landed. My object in collecting, and consequently also in presenting to the Society, this series of specimens, was to afford the means of comparing with each other the productions of the two great obsidian districts of Europe; those from Lipari, which are now on their table, with the Iceland suite already in their possession.

XXX. On the position of rocks in the geological series, whence the salt brine is derived, in the state of New York, North America

XXX. <i>On the position of rocks in the geological series, whence the salt brine is derived, in the state of New York, North America</i>

XIII.—Remarks on the Geology of Jamaica.

The detailed observations, which alone can establish on a secure basis the solution of those great geological problems, on which the hope of ultimately arriving at any satisfactory theory must of necessity depend, are, notwithstanding the rapid progress which geology has recently made, as yet confined to districts comparatively limited. The investigation of the order in which the mineral masses constituting the earth’s surface rest upon each other, and the inquiry how far that order is invariable,—whether the remains of successive races of organized beings, which characterize the different members of the geological series, exhibit in distant countries general features of analogy, or of distinction,—and how far the action of the various geological causes which appear to have operated in those localities with which we are best acquainted can be recognised in others,—are questions which have hitherto been principally confined to a few European countries. Even the very valuable materials which the comprehensive mind of Humboldt has accumulated, must be considered rather as indicating the extent of the field before us, than as having fully occupied any part of it. In the present state of our knowledge, detailed monographs of particular districts, although from their very nature in themselves dry and tedious, and little calculated to attract the general reader, must necessarily precede those extensive views, which are more delightful in proportion to the higher intellectual powers which they require for their developement. In the hope of contributing in the more humble manner towards the advancement of