256 Proceedings of the Royal Society to Take a Particular Example, Let V = 1000 Feet a Second, and Let P = the Density of Water, So That
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256 Proceedings of the Royal Society To take a particular example, let v = 1000 feet a second, and let p = the density of water, so that when h is the height of the column of water producing an equal pressure— " h=-. 9 v2 . If w be the weight of a cubic foot of water, p = toh = w— is the 6 g pressure on the square foot. Now, w = 72 lbs. and g = 32 and v2 = 1,000,000; 79 p = — x 1,000,000 lbs. on the square foot; 1 72 Or, x — x 1,000,000 tons on the square inch = 7 tons on the square inch. A pressure which the muzzle of a shot gun is not constructed to withstand, and the theory shows that this great pressure can be pro- duced even by a plug of snow or grease of the shortest length movable inside the barrel with the greatest facility. If the velocity of the ball or wad be less than that of sound the snow-plug is not driven out quite suddenly, and if the velocity be small enough the snow-plug is driven out before the ball or wad reaches the muzzle. i i 5. On some New Bases of the Leucoline Series. Part III. By G. Carr Eobinson and W. L. Goodwin. Monday, 7th July 1879. PKOFESSOR MACLAGAN, Vice-President, in the Chair. The following Communications were read: 1. Notice of Striated Eocks in East Lothian and in some adjoining Counties. By David Milne Home, LL.D. I know no more interesting problem in geology than the ques- tion, What was the great agency which brought the surface of Downloaded from https://www.cambridge.org/core. INSEAD, on 05 Oct 2018 at 19:31:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0370164600043765 of Edinburgh, Session 1878-79. 257 northern Europe into the condition in which it is now occupied by man? and it seems marvellous that geologists should not yet be agreed as to what that agency was. Our own country of Scotland is strewed with boulders, many of immense size, and which we allow have been somehow transported to their present sites from remote regions. Rocks on our hill-sides have been ground down, smoothed, and striated by ponderous bodies which have come against and rubbed upon them. Almost everywhere there are deep beds of clay, sand, and gravel forming knolls and elongated ridges, not only on low-lying districts, but even on our highest hills. These things have been attracting attention and provoking discussions for more than sixty years; but no explanation has yet been arrived at, which meets with general acceptance. Some geologists insist on the agency of an ice-sheet, like that in which Greenland is wrapped; Others stand up for local glaciers, such as exist in Switzerland and Norway. Some suggest icebergs and other forms of floating ice, in a sea which submerged the country. Each of these theories has its partisans; for no crucial test has been discovered to indicate which of them, or whether any, is well founded. The Transactions and Proceedings of our Society contain many papers regarding these phenomena. Of these papers, the earliest probably was by Sir James Hall, so long ago as the year 1812, and he was followed by M'Laren, Chambers, Fleming, and many other Fellows of our Society, who specially devoted themselves to this branch of geological research. The last paper published on this subject in our Proceedings, was by our colleague, Mr David Stevenson, who described a portion of the hill in East Lothian known as North Berwick Law, which was found by him to have been ground down, smoothed, and striated. These effects he ascribed to the agency of a glacier, which came from the westward against the hill, first smoothing the rocks on its north side by the heavy pressure of the ice, and afterwards scratching the smoothed surface by hard stones incased in and protruding from one side of the glacier. Mr S tevenson suggested that the glacier might even have been, and probably was, of such dimensions as to have enveloped the whole of the Law, which reaches a height above the sea of 612 feet. At the close of his paper Mr Stevenson expressed an opinion VOL, X. ^ G Downloaded from https://www.cambridge.org/core. INSEAD, on 05 Oct 2018 at 19:31:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0370164600043765 258 Proceedings of the Royal Society that if the rocks of Stirling Castle, Craigforth, and other places were examined, interesting and instructive traces of similar glacial action might be discovered. To this suggestion of an inquiry for cases of a similar kind, I am now here to respond, and with that view to lay before the Society an account of several striated rocks in East Lothian, Stirlingshire, and other places: I feel sure that Mr Stevenson himself will deem these cases not the less interesting, though they should warrant conclusions different from those he suggested. I. EAST LOTHIAN STRIATED EOCKS. The first of these which I mention, as the least complicated, are in the village of Linton. The rock is a claystone porphyry. Several smoothed patches of rock occur here, and two of these show striations on surfaces from 3 to 4 square feet in extent. One of these smoothed rocks is horizontal or nearly so; and on it the striae have a direction W.Jtf.W. and E.S.E. The other smoothed rock dips towards the north, at an angle of about 35°, and on it, the striae run due east and west. The difference between the directions of the striae of these two rocks, which are only a few yards apart from one another, may be accounted for by the fact that the same agent which produced striae in a certain direction on a horizontal surface, would, if that agent could be easily deflected, not produce striae in the same direction on a sloping surface. It would have less power to move up an inclined plane, but would move along it more horizontally. What the striating agent was here, and in what direction it moved, is made manifest by the following facts. Both patches of rock were, when I examined them, still partially covered by a coarse clay, full of stones or pebbles, many of which were hard and angular, but some were soft. There were among them bits of coal and limestone, which must have come from the westward, as in East Lothian there are no coal or limestone strata to the east of Linton. In one of the smoothed patches there were two small hollows or depressions, which had interrupted the continuity of some of the striae. These depressions on their inner surface showed a vertical wall on their west side, and a sloping wall on their east Downloaded from https://www.cambridge.org/core. INSEAD, on 05 Oct 2018 at 19:31:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0370164600043765 of Edinburgh, Session 1878-79. 259 side, indicating that the smoothing agent had partially entered the hollow, and had worn down a portion of the east side. Assuming that the general course of the striating agent here was from W.KW. towards E.S.E., it is quite intelligible that when this agent, if of a flexible nature, impinged on a rock surface dipping to the north, its direction would change so as to be more to the eastward. There is another rock of larger dimensions about a mile to the west of Linton village, on the line of the North British Kailway. It is about 25 feet in length and about 18 feet in height, and SOUTH N M/ EAS WEST EAST WEST Fig 1.—Rock on Railway, near Linton. presents a surface nearly vertical. It is on one side of a gully through which the railway passes, the rock being on the south side of the line. The rock was discovered and exposed to view, when an excavation for the railway was made into a thick bed of boulder-clay which occurred here. The rock now seen had previously been entirely covered by the clay. With the consent and the assistance of the railway authorities, I had an additional portion of the rock at its west end stripped of the clay, to the extent of several square yards, when more smoothing and striation was brought to light. Besides the rock which forms the lowest and principal part of Downloaded from https://www.cambridge.org/core. INSEAD, on 05 Oct 2018 at 19:31:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0370164600043765 260 Proceedings of the Royal Society the bank, there is a small patch of rock, about 10 feet long by 4 feet wide, at the top of the bank, also smoothed and striated. Both rocks dip rapidly, the upper one at an angle of about 55°, the lower one in its lowest part is vertical. The principal rock is AB on the preceding diagram (fig. 1) and the smaller is CD. The dip of each is indicated by the section at one side. The two rocks do not front exactly in the same direction. The lower rock fronts N". 11° W._ for two-thirds from its east end; but near its west end it fronts about K 30° W.