it appeared as if it had been imported; it did not seem to have been fossilised upon the spot. My attention was also directed to the material with which the ravine had been filled up, and the order in which it had been deposited. Uppermost was about 20 feet of clay with large boulders, very similar in texture and composition to the clay overlying the rock-material on either side of the ravine. The structure, composition, and thickness of the two deposits were so alike, that one could not help thinking that they must have been laid down during the same period of time. Beneath the clay with boulders was a finer kind of clay, containing stones of a much smaller size; and near the sides of the ravine it was well mixed with sand on fine mud, laid out in layers, rising gently to the edge of the rock at an angle of from 1 in 15 to 20. Lower down it contained more sand and less mud, sloping in the same bedded form to the sides, while in the centre there was no kind of stratification or order, the material consisting of large boulders intermixed with coarse clay and sand. Lower still, the section presented beds of small gravel and fine sand, with thin layers of coal, all finely stratified towards the edges, and rising with a gentle slope. The centre was composed almost wholly of gravel beds and sand, but having no appearance of stratification. The railway cutting showed material similar to this throughouti ts whole depth, which must be a considerable number of yards above the mine already referred to as having been cut through the sand beneath, at the bottom of the ancient ravine. The rocks which composed the sides of the ravine have been detailed on the margin of the Plate (fig. 3). It may not be unimportant to say a word or two upon the configuration of the surface at this point. It would be natural to expect here a more or less marked hollow, but it is in reality the highest portion of the ground in the immediate neighbourhood; the land falling on either side both towards the east and the west. Nowhere, on any part of its course, are any indications of the presence of the old ravine to be derived from the form of the present surface. The general inclination of the district is from east to west-from the summit at the Shotts Hills to the valley of the Clyde; and the rivers and streamlets generally flow in the same direction. The two streams of any consequence are the Tillon Burn and the Calder Water, already noticed; these both cross, at nearly right angles, this ancient ravine, which seems to have flowed in a general course from north to south. Conclusion. The facts furnished in this paper go to show-1st, That under the boulder-clay of part of Lanarkshire an ancient river channel has been preserved; 2d, That the course of this stream is from north to south, in which direction, as shown by mining operations, the water would still flow if the upper covering of clay were removed; 3d, that the present streams, flowing generally in an easterly and westerly direction, cross the buried watercourse at nearly right angles; and, 4th, that the early configuration of the district has been much changed by the deposit of the thick covering of "surface," and that the present streams have not, in the cases cited, resumed the former lines of drainage. IV. Notes on Chemical Geology. By ANDREW TAYLOR. (Abstract.) No true geological theory can be established which ignores the action of those physical and chemical forces which act on our earth in common with the other heavenly bodies. The essential unity of the cosmos has received fresh confirmation from the recent labours of astronomic spectroscopists. It becomes, then, the knight of the hammer not to ignore the bearings of such inquiries on his own science, the more especially as the great terrane revolutions manifested by the volcanic and earthquake activities of the last two years have given such investigations an universal interest. Recent researches have shown that most of our deductions on the internal condition of the earth have been founded on incomplete data. Arago's formula of the rate of increase of internal temperature, derived from observations made in the artesian well at Grenelle, does not hold universally. The increment of temperature appears to depend on a variety of conditions, such as the nature of the strata, their saturation or otherwise, the proximity of great bodies of water, and such like. Many observations go to show remarkable coincidences betwixt the presence of magnetic currents, and such phenomena as volcanoes and earthquakes. M. Perrey has observed that seismic. shocks occur with more or less violence according to the moon's distance from our planet. If these earth disturbances are the outcome of certain aberrations of those electric currents which we know daily pervade the whole surface of our globe, then accurate observations become necessary, that the character of these periodic perturbations of regular currents may be duly appreciated. Mr Mallet's observations go to prove that earthquake phenomena follow in pretty regular cycles of periodicityperiods of intense disturbance generally occurring at intervals of forty years, being most violent towards the close of the century; and when thus violent, the intensity appears to vary, in different hemispheres, with the month that the earth is nearest or furthest from the sun. That magnetism varies in intensity throughout the earth, as well as that it has done so in historic time, are two well-known facts. Over two well-defined regions the needle deflects from the true magnetic meridian in two distinctly opposite directions; and Arago has shown that within the last 200 years the direction of deflection has been proved to have altered both in London and Paris. If the sun is the source of the daily earth currents, as Dr Lloyd of Dublin has shown,* such facts will not surprise us, knowing as we now do the very variable character of the sun's body. The lines and periods of magnetic intensity follow the course of the sun until it reaches the full meridian. The epoch of maximum intensity of the current is earliest in islands or places nearly surrounded by the sea, and latest in the interior of great continents. The electricity of the earth is negative, and that of the atmosphere is positive. The cause of the separation of these two kinds of electricity is evaporation; and the intensity is usually greatest on the coasts of great continents, especially when the coast lines are in or near the meridian. The evaporation from the surface of the sea being much greater than from the land, the electricity will be most deficient at the former; hence, besides the electricity due from solar influences alone, there will be a flow of electricity from land to sea. Might not the drought of last summer, prevailing as it did nearly over the surface of our globe, have so deranged the equilibrium of the earth currents as to have caused internal action? That even well-known physical agencies can aid such currents in producing powerful effects on the crust of the globe is manifest from the fact that condensed steam, where 967 degrees of free heat becomes latent, is a source of electricity. The hydroelectric machine, according to Faraday, and other eminent electricians, gives static as well as dynamic effects of electricity, combining quantity with intensity. These effects are ascribed to the friction of the particles of steam and water against the sides of the outlet pipes. Thus the magnetic forces may effect great physical disruptions, as well as the quiet deposition of minerals in veins and the like. M. Necker, of Geneva, long agot showed that the curves of greatest magnetic intensity over the whole surface of the earth follow the bend of the different mountain ranges. Those districts most free from earthquakes are where the strata have been undisturbed, or nearly so, since their first deposition. Systematic observations made in many regions, and afterwards correlated, appear necessary ere we can adapt these interesting isolated facts to the purposes of geological theory. This is the legitimate work of local societies. Sir William Thomson has already called the attention of * Proceedings of Irish Academy, vol. viii. 1861-4. + Philip's Manual of Geology, 1855, p. 578. the Geological Society of Glasgow* to the importance of employing old bore holes for observations on underground temperature. I have to suggest that our Society embark in such inquiries in this neighbourhood. Bore holes might be taken as points of observation near the sea as well as in inland places. They might represent different varieties of rocks. An observation of the surface rainfall, as well as a little ingenuity in manipulating apparatus, might render observations of the conductive powers of the rocks practicable. Whether or no we enter on magnetic observations on the surface, I am not sure but such observations made in mines might, inter alia, go some way to elucidate coalpit explosions. With the aid of those of our members practically engaged in mining, such investigation might easily be accomplished. V. Closing Address for the Session. By ARCHIBALD GEIKIE, F.R.S., President of the Society. (Abstract.) Referring to the remarks which he had made on taking the chair of the Society at the beginning of the session, Mr Geikie again dwelt on the importance of local research. In illustration he pointed to the great drift deposits, some of which had been described in the papers of that evening. The complex phenomena of the boulder-clay were still imperfectly understood; little was known of the possible land-surfaces underneath the clay; the subdivisions of the clay and the history which each of them has to tell remained still in large measure uncertain. The evidence was slowly accumulating to show that the boulder-clay is not merely one deposit representing one epoch of Geological history, but a complex formation, containing the record of several epochs, or of the minor periods of one great epoch. But besides the old till or boulder-clay, the neighbourhood of Edinburgh furnished examples of later clays, sands, and gravels, the true import of which he could at present only dimly perceive. What was needed was the thorough and exhaustive examination of every section where any members of the drift series were exposed. This could only be properly done by local effort, and notably by the labours of such a Society as ours. The work that lay before the Society was first the thorough exploration of their own neighbourhood. A large proportion of the members of such a Society as this must necessarily be but imperfectly acquainted with science; he ventured to suggest whether it would not be possible to try the results of elementary class meetings-meetings where conversational lessons in the * Trans. Geol. Soc. Glasgow, vol. iii. 1868, p. 23. |