L. Proceedings of Learned Societies. GEOLOGICAL SOCIETY. [Continued from p. 245.] April 11th, 1894.-Dr. Henry Woodward, F.R.S., President, in the Chair. HE following communications were read :— THE The author described the results of an examination of the infold of Jurassic rock in the Urserenthal, undertaken in the hope of finding some definite evidence as to the relations of the marble, exposed near the old church at Altkirche, and the adjacent Jurassic rocks. Good sections are few and far between; for the comparatively perishable nature of the rock causes it usually to be masked by débris and turf. 6 6 The easternmost of the sections described occurs high up on the slopes north of the Oberalp road. Read off from the northern side it exhibits (1) gneiss, (2) phyllites with bands of subcrystalline limestone, etc.-Jurassic, (3) a little rauchwacke, (4)' sericitic' gneiss. The next section (about 250 feet above the St. Gothard road at Altkirche) gives (1) greiss, (2) covered ground, (3) slabby marble, (4) phyllite, (5) thicker mass of slabby marble, (6) phyllite, etc., (7) sericitic' gneiss. The third section (just above the church) runs thus, using numbers to correspond with the last:-(1) gneiss, (4) phyllite, (5) slabby marble, (6) phyllite, etc., (7) sericitic' gneiss. It must be remembered that on the slopes of the Oberalp farther south, between the sericitic' gneiss and the Hospenthal Schists,' another dark phyllite is found, generally considered by the Swiss geologists to be Carboniferous. The marble in the third section is in places distinctly banded with white mica, and passes on the northern side into fairly normal mica-schist and quartzose schist. The fourth section, about a mile away, on the left bank of the Reuss valley, gives a practically continuous section in phyllite and dark limestone, without any marble. In the fifth section, rather more than a mile farther, if any marble is present, it is very thiu and shattered. At Realp, about 3 miles farther, the next good section is obtained. Here the rocks go in the following order (from the northern side):-(1) gneiss; (2) phyllite and limestone; (3) subcrystalline limestone, looking very crushed; (4) the marble; (5) phyllite, etc.; (6) Hospenthal Schists. The last group of sections occurs near the Furka Pass. In the first, crossed by the high road, there is no marble, bu: a little rauchwacke on the southern side. The next one, on the slopes below the pass, seems to show two masses of the marble parted by a subcrystalline limestone like that at Realp, with phyllite above and below. Of the two masses of marble the southern one can be traced right across the pass, but the extent of the other is not so clear. Examination of the marble mentioned above shows in all cases that it has been considerably modified by pressure since it became a crystalline rock. The author discusses the evidence of these sections, and maintains that the hypothesis that the marble is an older rock intercalated by thrust-faulting among Jurassic strata leads to fewer difficulties than to consider it as belonging to the same system. In the latter part of the paper the results of a re-examination of the ravine-section in the Val Canaria, and of some studies of the south side of the Val Bedretto are described, which, as the author maintains, confirm the view already expressed by him, viz., that the schists with black garnets, mica, kyanite, dolomite, and calcite (the last sometimes becoming marbles) are not altered Jurassic rocks but are much older. 2. 'Notes on some Trachytes, Metamorphosed Tuffs, and other Rocks of Igneous Origin, on the Western Flank of Dartmoor.' By Lieutenant-General C. A. McMahon, F.G.S. In this paper the author notices the occurrence of felsite and trachyte at Sourton Tor; of rhyolite and of aluminous serpentine at Was Tor; and of a dolerite at Brent Tor in the exact situation indicated by Mr. Rutley as the probable position of the throat of the Brent Tor volcano. The author describes extensive beds of tuffs at Sourton Tor and Meldon, the matrix of which has been converted, by contact-metamorphism, into what closely resembles the base of a rhyolite, and which, in extreme cases, exhibits fluxion-structure, or a structure closely resembling it. The fragments included in this base are so numerous that six or seven different species of lavas may be seen in a single slide; this fact, and a consideration of the extensive over which these beds extend, lead the author to believe that these beds are metamorphosed tuffs and not tufaceous lavas. area He then describes some beds on the flank of Cock's Tor, which give evidence on their weathered surface of an original laminated structure by exhibiting a corded appearance like corduroy cloth. These beds are composed of colourless augite, set in a base which in ordinary light looks like a structureless glass, but which between crossed nicols is seen to be an obscurely crystalline felspar. The author compares these rocks with that portion of the Lizard hornblende-schists for which a tufaceous origin was proposed by De la Beche and other writers, including Prof. Bonney and himself. He shows that the Lizard schists and the Cock's Tor rocks agree in specific gravity and in some other characteristics; and he concludes that at Cock's Tor the first stage in the conversion by contactaction of beds of fine volcanic ash into hornblende-schist had been completed, and the final stage, due to aqueous agencies, had just begun. The paper concludes with some remarks on the relationship of the epidiorites to the rocks of volcanic origin, April 25th.-Dr. Henry Woodward, F.R.S., The following communications were read: : 1. Further Notes on some Sections on the New Railway from Romford to Upminster, and on the Relations of the Thames Valley Beds to the Boulder Clay.' By T. V. Holmes, Esq., F.G.S. The author alludes to his discovery of Boulder Clay on this new railway at Hornchurch (dealt with in a previous paper, Q. J. G. S. Aug. 1892), and describes the finding of more Boulder Clay close to Romford during the deepening and widening of a cutting there. The Boulder Clay was on precisely the same level as that at Hornchurch, a mile and a half to the south-east, and, like it, was covered by gravel belonging to the highest, and presumably oldest, terrace of the Thames Valley system. A portion of the silted-up channel of an ancient stream-course was also found in this Romford cutting. Its relations to the Boulder Clay could not be seen, as they were not in contact, but they were alike covered by the oldest gravel belonging to the Thames Valley system. The author discusses the probable direction of the flow of this stream-course, and the way in which it was superseded by the ancient Thames. After noticing certain points brought forward during the discussion on his former paper, he concludes with a criticism on the views to which Dr. Hicks inclines in his paper on the Sections in and near Endsleigh Street (Quart. Journ. Geol. Soc. vol. xlviii. 1892) as regards the age of those beds, asserting that they are, in all probability, simply River Drift of the Thames Valley system, and consequently post-Glacial, in the sense of being later in date than the Boulder Clay of Essex and Middlesex, 6 2. On the Geology of the Pleistocene Deposits in the Valley of the Thames at Twickenham, with Contributions to the Flora and Fauna of the Period.' By J. R. Leeson, M.D., F.L.S., F.G.S., and G. B. Laffan, Esq., B.Sc., F.G.S. The section described in this paper was exposed during the construction of an effluent from the Twickenham sewage-works to the Thames. Its length was about one mile. The beds exposed were :-(1) Coarse reddish-yellow gravels, coloured blue below, lying on an eroded surface of (2) Dark blue loam, varying in thickness, the greatest thickness seen being 3 feet, at a place where the bottom was not reached; (3) Dark sand; (4) Coarse ballast-gravel; (5) London Clay. The loam (which is quite a local deposit) yielded 8 species of mollusca and 14 species of plants, all still living in the neighbourhood. A number of mammalian bones referable to 7 species were lying just on the surface of the loam. Amongst the forms were bison and reindeer. The authors consider that the loam was deposited in a small lake, and they allude to similarities between it and a deposit described by Dr. Hicks as occurring in the Endsleigh Street excavations. 3. On a new Goniatite from the Lower Coal Measures.' By Herbert Bolton, Esq., F.R.S.E. LI. Intelligence and Miscellaneous Articles. A STUDY OF UNIPOLAR INDUCTION. BY PROF. DR. ERNST LECHER. THE HE first part contains historical and general observations, and shows that neither previous experiments nor the more recent modifications can settle this question. It appears that the BiotSavart law, of the action of a rectilinear conductor on a magnetic pole, is not in harmony with experimental facts. The second part contains a condensed account of the experiment of an electrometric proof of electrostatic charges of a rotating magnet. The author does not consider these experiments to be free from objection. The third part contains the experimentum crucis, and the decision of the question raised. A magnet is divided by an equatorial section in two parts, each of which can rotate separately. By means of suitable spring contacts it is possible to obtain from the two ends of the magnet an induction current which cannot possibly be due to a cutting of the rotating lines of force in the short fixed spring contacts. The current is easily explained if we adopt the view of Faraday, which, however, he afterwards abandoned, that the rotating magnet cuts its own fixed lines of force, and thus has an electromotive action.-Wiener Berichte, July 12, 1894. ON THE CIRCULAR MAGNETIZATION OF IRON WIRES. BY PROF. DR. IGN. KLEMENČIČ. The author investigated, in wires of soft and hard iron and of Bessemer steel, the extra currents which are formed on passing a current owing to circular magnetization. From the extra currents the susceptibility in a circular direction may be calculated by a formula of Kirchhoff. The susceptibility in an axial direction for different field-strengths was determined. The experiments showed that qualitatively the course of the susceptibility in both directions is pretty much the same. Quantitatively, however, the following difference is to be observed. With soft-annealed iron the susceptibility about the axis is less than in the direction of the axis. If the iron wire is hardened by a stress, the susceptibility in a longitudinal direction diminishes more rapidly than in the circular, and the behaviour observed for soft iron may even be reversed. Simultaneous experiments on remanent magnetism gave greater values for this with circular than with axial magnetization, especially in hard iron and steel. Repeated demagnetization with greater field-strengths increases the susceptibility for weaker fields, even with circular magnetization.- Wiener Berichte, July 5, 1894. THE LONDON, EDINBURGH, AND DUBLIN PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. [FIFTH SERIES.] NOVEMBER 1894. TH LII. Wave-Lengths of Electricity on Iron Wires. [Plate XII.] HE question whether the magnetic properties of iron are called into play under extremely rapid alternations of the magnetizing forces is an interesting one, and has received various answers. Hertz found negative results when he replaced one side of a rectangular copper resonator† by an equal iron wire; and in a later paper, on the "Finite Velocity of Electromagnetic Action", when he compares the rate of propagation along copper and iron wires, he concludes "that the rate of propagation in all wires is the same, and we are justified in speaking of it as a definite velocity. Even iron wires are no exception to this general rule; hence the magnetic properties of the iron are not called into play by such rapid disturbances " §. Dr. Oliver J. Lodge attacked the question by means of his experiment on the alternate path. In his Lightning Conductors and Lightning Guards' (1892), he remarks :-" But everyone will say and I should have said before tryingsurely iron has more self-induction than copper. A current * Communicated by Prof. J. Trowbridge. + Wied. Ann. xxxi. p. 429 (1887). § 'Electric Waves,' p. 113. Ibid. xxxiv. p. 351 (1888). Phil. Mag. S. 5. Vol. 38. No. 234. 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