Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/637

WOLF—LAVAS OF MOUNT VESUVIUS. 13 5. Granites. 6. Euritic porphyries. 7. Metalliferous deposits. 8. Greenstones. 9. Diluvial deposits. 10. Recent deposits.

The absence of the entire series of sedimentary rocks between the Dyas and the Diluvium leads to the conclusion that during the whole of this long period the region of the Altai was dry land, and that during the Diluvial period it was covered with water as far as the foot of the mountains. At this time an ocean, extending from the Glacial sea to the Ural, the Altai, and the Caspian and Black Seas, seems to have formed a boundary between Europe and the south and east of Asia. The absence of traces of glaciers, and, indeed, generally, of any vestiges of a glacial period, such as are so frequently observed in Europe, may be accounted for by the supposition that a current of warm sea-water, passing from the Mediterranean to the Glacial sea, took its course along the then existing Altaic coast. The Mammoths, remains of which have been found in some of the caves of the Altai, may have lived upon large flat islands rising out of the Diluvial sea. This sea having been removed, either by the upheaval of the land or by the draining off of its waters, left behind it numerous lakes, some of which still consist of salt water, and the climate acquired its present continental type. No traces of Tertiary, or Post-tertiary eruptions have been met with. The most recent eruptive rocks are Greenstones, which have broken through all the deposits, up to the metalliferous. Everywhere the old sedimentary strata are considerably upheaved and disturbed, but the periods at which these upheavals took place cannot at present be ascertained.

The metalliferous deposits in the west Altai are essentially uniform in type. They consist of sulphate of baryta or quartz, with a great diversity of metallic sulphurets, the products of the decomposition of which usually occupy the higher levels. The form of these deposits is very irregular, and they probably owe their origin to the filling up of fissures. They occur especially in the crystalline and sedimentary slates, and also in porphyry, but never in granite or greenstone; indeed, the last-mentioned rock has broken through a number of them. The metalliferous deposits of the low mountain- chain of Salair, in which granite is almost entirely deficient, form irregular beds in a talcose slate, but are evidently of later date than the rock in which they are imbedded. Sulphate of baryta predominates among their constituents. [Count M.]

On Chelonia from Eibiswald, in Styria. By Prof. C. Peters.

[Proc. Imp. Geol. Institute, Vienna, April 6, 1869.]

Professor Peters compares his new genus Chelydropsis, from Eibis-