No CrossRef data available.
Article contents
II.—On Enclosures of Glass in a Basalt near Bertrich, in the Eifel
Published online by Cambridge University Press: 01 May 2009
Extract
During a short holiday spent last summer in the Eifel, I was much struck with the occurrence of an extremely vesicular, dark-green glass in the lava at Bertrich, the most southerly point of the district at which traces of volcanic action are to be met with. It lies in the valley of the Uessbach, a little stream that flows into the Alf, a tributary of the Moselle. In all probability the ground on which Bertrich now stands was at one time covered with lava, and if the course of the Uessbach be followed for about a mile and a half above the town, thick patches of it may be clearly seen on either side of the present bed of the stream, all traces of it ceasing higher up the valley. It is well exposed in a quarry known as the Mühlrech, on the left bank of the Uessbach immediately below the high road to Kenfus, and about a mile above Bertrich. Here the lava exhibits a fine section about 90 feet high, but it is being rapidly cleared away for road metal. The quarry lies immediately at the mouth of a side-valley called the Müllischwiese, which commences near the foot of the Falkenlei, one of the three craters that overshadow Bertrich, and gently slopes down for a distance of about three-quarters of a mile into the valley of the Uessbach. The lava which can be thus so easily traced down to Bertrich is part of a great stream which in all probability commenced at some point in the Müllischwiese, and followed the course of the Uessbach, filling its channel to a considerable height. On its way it forms the well-known “Cheese Grotto,” about half-a-mile above Bertrich. It is difficult to determine the exact spot in the Müllischwiese at which the flow commenced, for the valley is now all under cultivation and much overgrown in places, and no traces of the flow can be seen except at the quarry to which I have referred, which is at the junction of the two valleys. Excavations have now been commenced immediately above the quarry by the side of the high-road; and the lava which is there being exposed is exactly similar to that seen below in the large quarry, only it is not so hard and compact, and presents a somewhat slaggy appearance.
- Type
- Original Articles
- Information
- Copyright
- Copyright © Cambridge University Press 1896
References
page 243 note 1 “Basaltgesteine,” p. 180. Bonn (1870).
page 243 note 2 E. Mitscherlich, “Ueber die vulkanischen Erscheinungen in der Eifel und über die Metamorphie der Gesteine durch erhöhte Temperatur”: Im Auftrage der Königl. Akademie der Wissenschaften zu Berlin herausgegeben von J. Roth, 1865, p. 29.
page 243 note 3 “Geognostischer Führer zu der Vulkanreihe der Vorder-Eifel,” p. 26. Bonn (1886).
page 243 note 4 Possibly he refers to the streak-like form sometimes taken by the glass; but his meaning is not clear to me. His words are: “Wahrscheinlich würden die geschmolzenen Augite nicht neben den unveranderten liegen und deren Körnerform in der dichten Lava eingeschlossen bewahrt haben, sich längliche Durchschnitte linsen-förmiger Körper darstellen.”
page 244 note 1 I am greatly indebted to Miss Aston, B.Sc., for assisting me with these experiments, which were carried out in the Chemical Laboratory of University College.
page 244 note 2 Still, Prof. Daubrée states that he fused olivine without much difficulty; this, however, was done under the influence of prolonged heat in a furnace.—“Géologie expérimentale,” vol. ii. Paris (1879), pp. 517–523.
page 245 note 1 Viz. pyroxenite and hornblendite.
page 245 note 2 Miss C. A. Raisin, B.Sc., has kindly shown me a piece of tachylitic glass occurring in a dark leucitic lava of unknown locality.
page 245 note 3 Loc. cit., p. 26.