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V. On the Revolutions of the Earth's Surface

Published online by Cambridge University Press:  17 January 2013

James Hall
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If such tremendous agents did in reality exert their influence in the Alps, it is not conceivable that other countries, situated lower, and composed of materials much more frail, could have been spared. We hear in fact of similar traces, more or less distinct, in all quarters of the globe. From the bones of animals, natives of the hottest climates, which are found over a frozen region of vast extent in the Russian empire, Pallas concludes, that an enormous torrent had transported their carcases across the ridge of Tartary.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 7 , Issue 1 , 1815 , pp. 169 - 211
Copyright
Copyright © Royal Society of Edinburgh 1815

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References

page 169 note * Observations sur la Formation des Montagnes, p. 71. Nov, Com, Petr.tom. xvn. p. 576.

page 178 note * As is very apparent upon some of the ridges last mentioned, as we see on the road to Dalkeith, just as we leave Edinburgh. Some ravines there present themselves in front, and on the right hand, descending the northern side of the ridge, and denoting a genuine diurnal action, in obedience to the mere action of gravity.

page 180 note * I have endeavoured, as yet without success, to make or procure an adequate representation of these forms; but I do not despair of overcoming this difficulty, and of being able, on some future occasion, to lay something of the kind before this Society that may not be unworthy of their notice. In this undertaking, I hope for the assistance of a very masterly artist, who is interested in the investigation, and who has already rendered me great services in this and other pursuits.

page 182 note * The only case which has as yet occurred to me, bearing any relation to the action here alluded to, arose from a cause seemingly quite insignificant. In a neighbouring county, a country house, situated upon the slope of a hill, was assailed by a sudden torrent of water, produced by the bursting of a thunder-storm on the hill above. The impetuosity of the stream was such, that it forced its way through the under storey of the house, carrying along with it quantities of sand and gravel, and stones of considerable bulk. Happening to be upon the spot a few weeks after the accident took place, I observed, that every stone, as it passed through the house, had left a rut or scratch behind it, upon the flags over which it passed.

page 183 note * They are also distinguished by this, that in the case of Slickenside, the rock has always upon it a crust of calcareous spar or zeolite, which seems to have occupied a vein. Both sets seem to have been the result of mechanical action. The slickenside has been produced, I conceive, in the Plutonic regions, at a time when the mass in general has been so far cooled, as to be solid, though sufficient heat has remained to keep the fusible matter, as carbonate of lime or zeolite, which filled the vein, in a state at least of semifusion; so that in the sliding of one mass on the other, it has acted like grease in the wheel of a carriage: this theory accounts for the parallelism of the lines of slickenside.

page 184 note * I am aware, that the usual mode is to describe the direction of a current at sea, by stating the point towards which it flows. But my object, on this occasion, being to trace the origin of these currents, I have been induced to follow an opposite mode, and in general to denote the course by the point from whence the stream has been supposed to flow. In the following descriptions, the principal object of which is to mark the place of each specimen, I have frequently omitted the direction, in order to avoid interruption. But these directions have been carefully observed, and may be seen by turning to the page at the end of this paper, where they are all placed in one column, each opposite to the name of the spot, and to its number.

page 185 note * Since this paper went to press, the valuable specimen here mentioned has been almost entirely concealed by the mettle of a road thrown upon it. The rock, however, remains entire, and may be cleared by any future observer.

page 190 note * Since this paper was read, the signal-house has been removed, and its foundation only is now visible.

page 194 note * It has also been alleged, admitting these dressings to have been the work of flowing water, that the action may have taken place at the bottom of the sea. and that the rock has since been elevated into its present position. Subscribing, as I do most heartily, to the doctrine of elevation, as advanced by Dr Hutton, I am far from denying, that the very case here supposed, may frequently have happened; I even conceive that it must have occurred occasionally. I should not, therefore, object to this explanation of a dressed rock, that stood single in an extensive district. But that is by no means the case in the present instance: the phenomenon is far from single; it is surrounded, on the contrary, by facts, and classes of facts, calling for an explanation. This is afforded, if I do. not deceive myself, by the hypothesis advanced in this paper. But the explanation just alluded to, would account for the dressed rock alone, and would be altogether inapplicable to the other classes of phenomena; by such a partial solution, we should therefore lose all the advantage derived in the theory proposed, from the mutual light which the large features and the small ones have thrown upon each other.

This explanation, too, would require no less an effort of imagination than ours; in fact, the two suppositions do not differ as to the magnitude of the exertion employed, but only as to the place of its original action, which we have conceived to lie somewhere to the westward. An elevation such as would carry this district from the bottom of the ocean into its present position, could not fail, (as we have endeavoured to prove in the first part of this paper), to be performed by starts, and consequently to produce waves. If the whole elevation took place at once, it would be of magnitude amply sufficient to fulfil, in some other quarter, all the conditions of our hypothesis.

It might also be alleged, that the elevation was performed only in part, when the dressings took place; and that a further rise had carried the mass, on a subsequent occasion, to where it now stands; but nothing here seems to justify such an intermediate supposition. All the diluvian facts in this neighbourhood, that have come under my observation, concur in denoting one inundation overwhelming the solid mass of this district, which had been elevated into its present position by some still more ancient revolution of the same sort; this inundation being the last catastrophe to which it has been exposed.

Having endeavoured to illustrate the appearance of the dressed surfaces, by referring to abraded rocks in the beds of rivers, I find that some gentlemen, who had heard but a partial statement of my views, conceived it to be part of my supposition, that these dressings, like those in a river, were produced by water acting for a long time. But this is by no means my view; my theoretical notions limit the action upon the hill under examination, to the passage of a single wave, embracing a period of time that could only be expressed in minutes: but during (hat short time, I conceive the water to have been urged forward with such force, and to have carried with it so many powerful agents, that it has produced effects equal to the work of ages under other circumstances.

page 209 note * Since the first part of this paper was printed, a very familiar circumstance has presented itself, which affords a clear illustration of this great natural operation. When a mason is preparing common lime for building, he lays the burnt limestone in a heap, and throws water upon it; after this, some time elapses before any action is visible, before the lime, as it is said begins to fall; in this interval the sand, which is to be mixed with the lime, is thrown upon the heap, so as to cover it completely, and the surface is made smooth and uniform by repeated blows of the flat of a spade. Soon after this, a heave takes place from within; the lime swelling, raises up the sand, and divides it by numberless rents, which becoming wider and wider upwards, as the heave advances, a representation in miniature is produced, of an alpine district.