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Groye*. It is stated by the latter as being about 1200 fathoms in length, and 600 or 700 in breadth, whilst it rises to about 200 fathoms above the level of the sea. It is composed of basalt, which, as we trace it downwards, is seen to pass into a very crystalline greenstone, and is covered by an amygdaloidal wacke, the cells of which, probably from the decay of the rock, are empty near the surface, but in the interior are filled with calcareous matter. The latter is sometimes so diffused through the substance of the rock, that it forms with it a kind of breccia, and even swells out into nests or geodes of considerable size, imbedded in the midst of the tuff. Shells are also contained in this formation, and serve to connect it still more closely with the limestone covering it, the recent origin of which may be inferred from the existence in it of bones of ruminating animals. This limestone is compact, and passes into a siliceous kind of rock, probably a chert, called by Haüy quartz agate calcifère, which M. Marcel de Serres considers to be posterior to the second freshwater formation of Cuvier and Brongniart, an inference he is disposed to extend to the volcanic products of the department of Herault t.

The latter constitute a chain for the most part continuous, which pursues a very determinate direction from north to south.

The volcanic formation indeed commences at the most northern extremity of the department, where it is seen in its greatest force, attaining at Escandolgue an elevation of 667 metres (above 2000 feet); it is prolonged almost without interruption as far as the centre of this province, assuming its largest development about Neffier, Caux, Pezenas, and St. Thibery; and it extends from thence to the south, passing by Agde, and losing itself in the bed of the Mediterranean at the fort of Breseau.

This band or chain of volcanos then traverses the whole department, exhibiting its greatest width at once at the northern portion and at the centre of the department. It is everywhere loftier than the primary chain, and its ramifications are likewise more numerous.

See Journ. de Phys. vol. Ixxxii. Ixxxiii. † Marcel de Serres sur la Constitution Géogn. du Dép. d'Herault.

The rocks of which it consists bear in many places evident marks of fusion, and are manifestly connected with the volcanic chain already described, which extends northwards through the department of Ardeche to that of Haute Loire and Cantal, terminating, as we have seen, in the district around the Puy de Dôme.

The only one of these rocks which it has fallen to my lot to visit is that of St. Loup, an extinct volcano close to the sea, about a league to the north-west of Agde, a town placed at a distance of about twelve miles west of Cette in Languedoc.

Its crater, which is of considerable size, has emitted two currents of lava, on one of which the town of Agde itself is erected; whilst the other, having taken the direction of the sea, has formed a neck of land, as well as a little island at a short distance from the shore.

Marcel de Serres seems to regard the rock of Montferrier near Montpellier as belonging to the same epoch and formation, but I found it to consist wholly of compact trap, and therefore regard it of much greater antiquity.

Volcanos of Germany.--Modern ones in the Eifel.-General charactersdistinguished into those of the Upper and Lower Eifel.-Upper Eifel -Gerolstein-Mosenberg-Bertrich.-Lower Eifel-Lake of LaachLava of Niedermennig-Basin of Rieden and others.-Trass of Brühlits origin considered.—Crater of Rodderburg.-Antiquity of the Eifel volcanos discussed.—Ancient volcanos-near the Rhine-Siebengebirge. -Quarries of Obercassel-Vogelsgebirge-Westerwald.-Basaltic knolls near Eisenach-Pflasterkaute-Budingen-Blaue Kuppe-MeisnerHabichtswald-Steinheim-Odenwald-Black Forest - near Freyburg— near the Lake of Constance-Wirtemburg-Rhöngebirge-Fichtelgebirge-Kammerberg near Egra-Toeplitz-Erzgebirge-Riesengebirge -Moravia-near Hof, near Banow.-General remarks on the Volcanic Rocks of Germany.

AFTER this general description of the volcanos of France, I shall proceed to a short sketch of those which occur distributed over various parts of Germany.

Although active volcanos are not found in any part of that extensive country, and the recognition of those which are extinct dates only from the last century, yet no one familiar with this class of phænomena can return from a visit to their principal localities with any more doubt as to their former existence, than an American who had witnessed the burning mountains of his own hemisphere, but had never heard of those in Europe, would entertain with respect to the real nature of Vesuvius, if landed at its foot when it chanced to be in a tranquil state.

This remark applies to no case more completely than to that of the rocks which occur in a district commonly known by the name of the Eifel, situated between the Rhine and the present frontier of the Netherlands *.

This country is bounded on the south-east by the Moselle,

* This account of the Rhenish volcanos is principally drawn (where the reverse is not stated) from observations made by myself during a tour in that country in the summer of 1825.

on the north-east by the Rhine, on the west by the Ardennes and the other mountains round Spa and Malmedy, and on the south by the level country about Cologne.

The fundamental rocks which come to view are of a schistous character, and with their accompanying shales and sandstones, were styled by myself, in common with others who had described the district, greywacke.

Later observers, however, have spoken of them in a less vague manner, Lyell regarding them as constituting the inferior members of the carboniferous series, whilst Professor Sedgwick and Sir Roderick Murchison consider them as belonging partly to the Devonian and partly to the Silurian system.

It is at least certain, that the saccharoid magnesian limestone, containing trilobites, and other fossils of the same age, which is found associated with this formation, places it very low in the series of the palæozoic strata.

These rocks, in a few places, support horizontal beds of what appears to be the second or variegated sandstone formation. Scattered, however, over the greater part of the district alluded to, are a number of little conical eminences, often with craters, the bottoms of which are usually sunk much below the present level, and have thereby in many cases received the drainage of the surrounding country, thus forming a series of lakes, known by the name of “Maars,” which are remarkably distinguished from those elsewhere seen by their circular form, and by the absence of any apparent outlet for their waters.

Steininger *, a geologist of Treves, who has published the most circumstantial account of the whole district that has yet appeared, distinguishes these craters into three classes.

The first includes those, properly speaking, known by the name of “Maars," -volcanos which have ejected nothing but loose fragments of rock with sand and balls of scoriform lava. In this class are :- 1. the Lake of Laach ; 2. the Maar of Ulmen ; 3. three Maars at Daun; 4. two at Gillenfield ; 5. one at Bettenfield ; 6. one at Dochweiler; 7. one at Walsdorf; 8. one at Masburck. Nos. 6 and 7, however, have fallen in.

See, for an enumeration of his works, the Appendix,

The second class is distinguished from the preceding in consisting of those which have ejected fragments of slag, sometimes loose, and sometimes cemented together into a paste. Of this denomination are:-- 1. three craters at Gillenfield ; 2. two at Bettenfield; 3. one at Gerolstein; 4. one at Steffler; 5. two at Boos; 6. one at Rolandseck.

The third class includes such volcanos as have given out streams of lava as well as ejections of loose substances. Of these latter we may mention :2. two at Bertrich (one very small); 3. one at Bettenfield (the Mosenberg); 4. one at Ittersdorf; 5. one at Gerolstein ; 6. one at Ettringen.

The above enumeration comprehends, probably, the most interesting of each class; but it must not be regarded as by any means complete, for Dr. Hibbert has added considerably to the list, within the limits of that district alone to which he has confined his attention *.

Geographically considered, these craters may be classified otherwise, as they belong to two districts, distinguished by the names of the Upper and Lower Eifel; the Upper lying to the south-west, in the angle between the river Moselle and its tributary the Kyll; the Lower Eifel near the western bank of the Rhine, extending to Mayence, where it is separated from the former volcanic district by the older rocks of the country.

The following description will apply to the volcanic formations in both these localities.

The sides of these craters, wherever their structure was discernible, appear to be made up of alternating strata of volcanic sand and fragments of scoriform lava, dipping in all directions away from the centre at a considerable angle; and the same kind of material has in many instances so accumulated round the cones, as to obliterate in great measure the hollow between them, and to raise the level of the country nearly up to the brim of the craters.

The formation of these cones seems likewise to have been, in some instances, followed by an ejection of substances of a pumiceous character, and the same kind of material (whether