Limestone Pebbles Research Articles

IV.—Pebble Ridges

As a contribution to our knowledge of the formation of these very interesting “natural embankments of the sea,” I may point to a little bay in Anglesea, immediately westward of the Bryn Ddu Limestone quarries on the north-east coast of Anglesea, about two miles and a half westward of Puffin Island. This little bay is not more than about a furlong across, and may be roughly described as semicircular in form, lying nearly due west to east from point to point. From being in miniature as it were, the ridge can be readily studied, and it is very striking to see how, commencing in the westward as a beach, it gradually rises into a ridge having very steep sides. No less remarkable is the way in which the stones increase in size as the ridge does in height. At the west end it may be described as composed of Limestone pebbles, with here and there a boulder, while at the east end it is built up almost entirely of large limestone boulders and blocks, many containing from one to two cubic feet and some more. Intermixed there are boulders from the size of the closed hand and upwards. The larger blocks are sub-angular and rounded, and no doubt get gradually worn down smaller and rounder, until they become “boulders.” by being moved about, by the sea; but some on the other hand, being thrown over on to the back of the bank, cannot be further affected by the waves. In this ridge, as I have pointed out is the case with the Chesil Bank, the stones follow the law of the bank itself, the largest being collected to form the highest part of the bank, which in both occurs where the wave-action is most intense.

Notes on the Glacial Drift near Ripon

The Beds of Glacial Drift near Ripon seem to be of three distinct ages, probably separated from each other by long intervals of time. The earliest of these is a bed of Black Boulder Clay on the south side of the valley of the Laver, a section of which has been exposed in a quarry of Magnesian Limestone near Oldfield. Upon the eroded surface of this lies the Brown Boulder Clay, which is the common Drift of the district. Over this again, on each side of the Ure near Ripon, is a mass of sand, clay, and gravel, derived partly from the Boulder Clays and partly from the disintegrated New Red Sandstone against which it rests. The sand is sometimes red, sometimes white, and occurs in lenticular masses, or in thin contorted beds. Of the same age is a Gravel Deposit at Wormald Green, at the east side of the stream, which, in its false bedding and the roughened surfaces of the Limestone pebbles, exhibits clear traces of having been washed out of older beds and re-deposited. It is to a fact belonging to the second of these beds, the Brown Boulder Clay, that I wish to draw your particular attention. On its eastern side the Boulder Clay spreads widely over the vale of York, and is mixed with or overlaid by more recent deposits. But its western side is more or less sharply defined, and lies upon the eastern edge of a very singular valley, which intersects the direction ...

Ripple-Drift in Mica-Schist

Of all English geologists, Mr. Sorby has been at once the most indefatigable and the most successful in the study of the microscopic structure and metamorphic conditions of rocks. The brief abstract furnished us by the Geological Society, which we print at p. 231, gives but little idea of the importance of the paper Mr. Sorby read last month. It gives, it is true, the pith of the subject, but so short and inexplanatory a paragraph is not likely to attract such attention as the paper deserves. Those who have the pleasure of Mr. Sorby's acquaintance know how persistently he works at anything puzzling which comes in his way. He never leaves it until he has got to the solution of the riddle. It happened some time ago, when in Germany, at the meeting of savants at Speyer, on which occasion he transmitted an account of the proceedings, with some notes on meteorites and sponges (see Vol. IV. p. 501), that Professor Blum presented him with a specimen of the singular conglomerate known as the “nagel-flue.” This conglomerate, which occurs in some places in Switzerland, consists of hard limestone pebbles, the ends of some being impressed into the substance of others,—a condition hitherto inexplicable, although Blum, Von Dechen, Escher von der Linth, Nöggerath, Daubrée, and others have essayed opinions and suggestions, some of them attributing the impressions to merely mechanical, others to purely chemical action.

On Impressed Limestone Pebbles, as Illustrating a New Principle in Chemical Geology

In certain conglomerates, consisting chiefly of pebbles of limestone, met with in various places on the Continent, and notably in the so-called Nogelflue in Switzerland, a very curious and interesting phenomenon has been observed: one pebble penetrates into another, sometimes to such an extent that it nearly passes through it, without there being any apparent fracture. Usually, however, the impressions vary in depth, up to half-an-inch or more, and into them another pebble accurately fits; and when it is removed a hollow is left, as if it had been pressed into soft clay. Much attention has been paid to this phenomenon in Germany and France, and various theories have been propounded, none of which in my opinion are satisfactory; but it has attracted so little attention in our own country, that I have met with very few of my countrymen who ever heard of the subject. On studying the German and French literature related to this question, references to which may be found in a Paper of mine published in Germany,* I soon became convinced that the facts could not be explained in a satisfactory manner on any known chemical or mechanical principles, and I therefore was induced to investigate the question with the view to ascertain whether it would lead to some new physical principle. One thing led to another, until I was led into a wide and almost unexplored branch of research, which in the course of time enabled me to establish the direct correlation of mechanical and ...