Undulating Plain Research Articles

How Anglesey became an Island

T he structure of the low ground of Caernarvonshire within three or four miles of the Menai Straits in almost all respects resembles that of Anglesey, both in its geology and physical geography. The Menai Straits divide the two regions; but carboniferous rocks form the larger part of either shore, and the Straits may be considered simply as a long shallow valley, the bottom of which happens to lie beneath the level of the sea. The question thus arises. At what epoch and by what means was Anglesey separated from the mainland? The whole of Anglesey is low; and only one steep escarpment, a minor one, occurs in the island—that of the Old Red Sandstone overlooking Traeth Dulas, which rises abruptly above the tidal flat of the Traeth to the height of about 250 feet. (See Map and Section Pl. XIV.). The entire island may, indeed, be looked on as a gently undulating plain, the higher parts of which attain an average elevation of from 200 to 300 feet above the level of the sea; while most of its principal brooks and small rivers run north-east and south-west, in depressions with gently sloping sides; and only one inland valley, with the same trend, is of any marked importance, namely that of Malldraeth Marsh, in which the small coalfied lies. There are, however, a few exceptions to the average levels mentioned above—the summit of Holyhead mountain being 709 feet, and Garn, near Llanfairynghornwy, 558 feet above the sea, while the greatest elevation

On the River-courses of England and Wales

In the following paper I propose to show the origin of many of the principal rivers of England and Wales—that is to say, what are the special geological causes the operation of which led them to flow in the general directions they now take. I am not aware that any attempt has heretofore been made to do this on a large scale, though I have already done something on the subject with regard to the rivers of the Weald, in which line of argument I was afterwards followed by Mr. Foster and Mr. Topley. I shall begin the subject by a rapid summary of certain physical changes that affected the English Secondary and Eocene strata, long before the Severn (leaving the mountains of Wales) took its present southern and south-western course along the eastern side of the palæozoic rocks that border that old land. About the close of the Oolitic epoch the strata of these formations were raised above the sea, and remained a long time out of water; and during that period those atmospheric influences that produced the sediments of the great Purbeck and Wealden delta were slowly wearing away and lowering the land, and reducing it to the state of a broad undulating plain. At this time the Oolitic strata (till abutted on the mountain country now forming Wales and parts of the adjacent counties. They also completely covered the Mendip Hills, and passed westwards as far as the hilly ground of Devonshire, running out between Wales and

Kant's View of Space

IN answer to my invitation, Mr. Lewes now “freely admits that Kant nowhere speaks of Space and Time as ‘Forms of Thought,’” but still contends that ‘Kant would not have disclaimed such language, as misrepresenting his meaning.’ As well might he argue that although Euclid never uses the word epipedon (our English word plane or plain), to signify a curved surface (eπιφανeια), he would not have remonstrated against the use of the term cylindrical epipedon or conical epipedon, to denote the surface of a cylinder or cone, in a professed exposition or criticism of his Elements of Geometry, because in common life we speak of rough or undulating plains, or because a plane admits of being bent into the shape of a cylindrical or conical surface. I think the ladies who are getting up their Planes and Solids at St. George's Hall would be of a different opinion from Mr. Lewes in this matter, and with good reason on their side.

On the working together of igneous and denuding agencies in the formation of scenery

In noticing the general outlines of a country, the lofty mountain ranges intersected by deep gorges and winding passes, the giddy precipices and overhanging crags, the casual observer might naturally suppose that here nature had, in times long gone by, exerted energies and put forth forces now no longer exerted with equal intensity, might attribute their formation to cataclysms and paroxysmal efforts; while, in the spreading valleys and undulating plains, he might as readily fancy that here repose had ever reigned, and that no convulsion had ever disturbed the peaceful district. To the careful student of the various modes in which such phenomena are wrought out, it however soon becomes apparent that nature’s greatest works are accomplished, not by any prodigal and paroxysmal expenditure of force, but by the long and continued application of means at first sight appearing totally inadequate for producing such results. Our loftiest mountains are raised to their present altitude, not by any sudden exertion of volcanic agency, but by a slow, gradual, and, for the most part, imperceptible process of elevation; while many of our deepest gorges are simply the effect of the slow, but certain, wasting powers of running water. In no case, however, are these results brought about by any one cause. The mountain range has the form of its features finished by atmospheric and other denuding agencies, while some fissure, or other inequality, first directed the stream in the course it has since pursued with such marked effects. It, however, appears to

I. The Old or General Glaciation of the Country

The phenomena from which the history of the first part of the drift period is compiled, are the rounded and scratched rock surfaces and the boulder-clay. We may first attend to the nature and extent of these phenomena, and then proceed to investigate the conclusions to which they appear to point. 1. Rounded and Striated Rocks. To the practised eye the surface of Scotland presents almost everywhere a peculiar rounded or moulded outline which the geologist recognises as a characteristic result of ice action. It is traceable in the wildest scenery of the Highlands, and throughout the bare rocky Hebrides; the uplands of the southern counties with their grey granite hills and solitary tarns, show the same features. But nowhere do we see this swelling contour more complete than along the wide central valley from the shores of the Firth of Clyde eastward to those of the Forth and Tay. The high grounds of Renfrew and Ayrshire, stretching north into the heights of Kilpatrick, and thence into those of Campsie and the Ochils, abound in that union of prominent yet rounded crag and gently curving hollow which indicates the passage of the ice-sheet with hardly less clearness than the ripple on the shore tells of the retreat of the sea. On the isolated eminences also which rise so conspicuously from the undulating plains of this district the same outline may be traced. We see it on the rock of Stirling Castle, on the heights of Linlithgow, on the group of This 250-word extract was created in the absence of an abstract

On the Geology of Catalonia

The general aspect of the Spanish Province of Catalonia is a series of hills, which take a direction from the north-east to the south-west, nearly parallel to the coast; they are separated from each other by undulating plains or valleys of nearly the same width as the ridges, varying from five to twelve miles. These hills occasionally rise to a considerable elevation, from 2000 to 3000 feet. As great disturbance has taken place near the chain of the Pyrenees, these parallel ridges do not assume their predominant character nearer than about twenty miles from the base of these mountains; but even beyond this distance, they are considerably disturbed here and there throughout their extent by igneous action and the protrusion of masses of granite. The pass of the Pyrenees by Bellegarde to Jonquera represents the general character of several other ridges in the province, the base being granite, covered by gneiss, and surmounted by very thick deposits of schistose beds, with occasional masses of limestone and red marly sandstone.