urge the vacuity of the arteries after death as an objection to the doctrine of our immortal Harvey.

How far temporary accumulations of blood in the pulmonary artery are a source of disease, I leave to the decision of time. Yet I must say, that Dr. Traill's coinciding with my views on the subject, has made me not a little sanguine, that my pathological speculations are founded upon a substantial basis; and I cannot refrain acknowledging that I am gratefully sensible of my obligations to Dr. Traill, for his kindness during the above inquiry, as well as at all other times.

ARTICLE XII.

Memoir illustrative of a general Geological Map of the principal Mountain Chains of Europe. By the Rev. W. D. Conybeare, FRS.&c.

(Continued from vol. v. p. 359.)

CHALK FORMATION.

This formation appears to stretch through an area of great extent, occupying the interior of the grand European basin, reaching probably from the banks of the Thames to those of the Dniestr; or if we attach credit to the observations of Dr. Clarke, even to those of the Don. It is not, however, to be understood, that its beds can be traced continuously throughout the borders of this area, so as to present an uninterrupted basset edge; for this holds true of its western limits in England and France alone. In the central portions of Europe, it is greatly concealed partly by the overlying of the more recent tertiary deposits, and partly by the vast accumulations of diluvial debris, which veil from observation the native rocks throughout so large a portion of the north of Germany.

(A.) Shores of the Baltic.

The northern limit of this area may be traced in the line of the Baltic on the island of Rugen, where chalky cliffs present themselves on its northern coast, being found also on the neighbouring continent, in Pomerania and Mecklenburg. Hence the line appears to pass to the south of Sweden, where a small chalk tract occurs near Malmo, crossing to the opposite coast of Zealand, and including the small isle of Mona on the south. Some account of these localities may be found in De Luc's travels.

From Mona, the line of the chalk has not been traced: it probably traverses Holstein (where it is said to occur, probably

near the gypsum of Kiel) to the mouth of the Elbe, and thence crosses the German Ocean.

(B.) England.

This formation first exhibits those white cliffs which have been supposed to have bestowed on our island one of its ancient appellations at Flamborough Head, in Yorkshire; and thence stretching to the south-west, traverses England diagonally, till it reaches the British Channel, in Dorsetshire, being broken through, however, in its course by the estuaries of the Humber and the Wash. The greatest breadth of this formation is in Wiltshire and Hampshire, where it expands into those vast plains which Pennant has appropriately termed the great central Patria of the English chalk. Hence it detaches two branches to the south-east, viz. the North Downs through Surrey and Kent, to the Dover and Folkestone cliffs, and the South Downs through Sussex, to those of Beachy Head. The interval between the North and South Downs is occupied by the formation of sand, &c. inferior to the chalk, constituting what has been called the denudation of the Weald, and extending into the Boulonais on the opposite side of the channel.

The areas lying between these branches and the main diagonal chain are occupied by basins of the more recent tertiary deposits, viz. the basin of London, between the main chain and the North Downs, and the basin of the Isle of Wight, between the main chain and the South Downs. The south side of this latter basin is skirted by a curvature of the main chain towards the east, deflecting it so as to cause it to run through the peninsula of Purbeck and the Isle of Wight. This deflected portion of the chain is remarkable from the circumstance, that its strata are throughout greatly elevated, and generally nearly vertical; while in other places the angle of the beds of this formation with the horizon rarely exceeds 20 or 3°.

The height of the chalky Downs in one instance (Inkpen, in Hampshire), exceeds 100 feet, and is often between 800 and 900 feet above the level of the sea.

(C.) France, and the Netherlands.

This formation occupies on the northern coasts of France, an extent exactly corresponding to its line on the southern coast of England. At the mouth of the Seine, its outer edge (which reposes on green sand, having oolite and lias in the neighbourhood) turns south, and so continues to Blois, where the formations above the chalk overlie and conceal its southern extremity: it reappears at Montargis, and turning again north (for the whole chalk district of France forms a sort of Cape protruding to the south of its general line), runs east of Troyes, Rheims, and Valenciennes, having the green sand, oolites, and lias, on its east, till it approaches the latter town, where most of these

formations are wanting (an instance of want of conformity in their direction), and the chalk, with a few beds of green sand, there called Turtia, rest horizontally on the truncated edges of the coal formation, which extends thence along the banks of the Meuse to Liege and Aix; the coal is here even worked beneath the chalk. North of Valenciennes, the edge of the chalk appears to trend to the east, but it is generally overlaid by the sandy superstrata through the Netherlands it may, however, be seen on the south of Maestricht, and at Henri Chapelle near Aix.*

(D.) Germany.

As in the Netherlands we have traced the chalk skirting the north border of the coal fields which repose against the transition chains, so we find on crossing the Rhine the lower beds of the chalk formation (craie chloritée verdatre) similarly placed in the prolongation of these lines in Westphalia, i. e. to the north of the coal fields of the Rahn extending from Unna by Soist to Geseke and Lichtenau, Thence, after an interruption caused by the alluvia of the Lippe, it reappears near Domhagen and Paderborn, and forms at the foot of the muschelkalk a series of little escarpments, which extend by Schlangen, &c. beyond Hilter, in Osnaburg.t

To the north of the secondary hills of Westphalia, the whole district is well known to present the appearance of an uniform and vast sandy heath, covered with a deep accumulation of diluvial gravel, in the midst of which occur enormous rounded blocks of granite, for which a source cannot be found nearer than the opposite shores of the Baltic-thus exhibiting one of the most striking problems submitted to the investigation of geology. The great mass of this gravel, however, consists of chalk flints, well marked, and bearing traces of all the characteristic fossils at least nine-tenths of the whole consist of these; a sign that the parent formation can be at no great distance. In such a tract, a rock in situ is like an oasis in the desert; at Luneberg, however, the fortifications are partly constructed on a rock of gypsum, and about a quarter of a mile hence, on the left of the road to Hamburg, the writer of this article was gratified by detecting a chalk-pit which had escaped the attention of former observers: it contains the usual alternation of flints, and affords good specimens of the inoceramus, echinites, and most of the characteristic fossils,

:

Dr. Boue also notices a similar patch of chalk at Mount

There are other chalky districts in the south-west of France connected with the basin of the Garonne, but these being apparently unconnected with the great chalky area, occupying the interior of the principal European basin, will be mentioned in the close of this article.

+ I copy these localities from an excellent article of Bouè's on the Geology of Germany, which appeared in the Journal de Physique for May, 1822, I have to regret that I was not earlier aware of the existence of this article,

Lindon, near Hanover, and several others between that town and Goslar, especially in the hills called Elbergebirge between Grasdorf and Unter Elbe. My friend, Prof. Buckland, informs me, that in this tract the chalk forms highly included ridges, like that called the hog's back, near Guildford. There are also seve ral detached patches of the lower beds of this formation between Goslar, Halberstadt, and Enedlinburg (see Bouè). From their position these localities should seem to be occupied by outlying masses on the south of the general boundary of this formation; but Dr. Bouè mentions another point, Prenzlow on the Ucker See, in the north of Brandenburg, where it probably appears by denudation in the midst of the tertiary formations.

I do not here mention the chalk said to occur near Ratisbon which must be referred to a distinct basin, (that, namely, extending from the north foot of the Alps to the Bohemer Wald), nor, for similar reasons, the traces of this formation, which, according to Bouè, exist throughout the basin of Bohemia, and even in the valley of the Elbe, near Dresden, placing these as supplementary articles at the end of this sketch, of the course of the chalk through the principal European basin.

In pursuing then the southern boundary of this basin, it does not appear to have been noticed between those points north of the Hartz to which we have already traced it, and the district on the north of the Riesengebirge, where it reappears in Lusace and Silesia, e. g, on the west of Lawnberg and Lauben, &c.

(E.) Poland.

:

This formation here constitutes a line of hills running parallel to the Carpathians; it is finely exhibited at Cracow it contains abundant flints, affords the usual organic remains, and rests on green sand it was here examined by Prof. Buckland. Hence, passing by Lemberg, it appears to extend into Russia.

(F.) Russia.

The chalk is here exhibited according to the map of M. Beu dant, in several detached points, on the north of the Dneistr to the north-east of Zaleszyky, between the 25th and 28th parallels of long. from London.

Hills of chalk were noticed by Dr. Clarke at Kasankaiya on the Don, and the town of Bielogorod, signifying the white city, is said to take its name from white hills of the same substance in its neighbourhood. Engelhardt observed chalk, containing its usual flints and fossils, even in the Crimea.

Mr. Strangways is, however, of opinion, from more recent examination, that the supposed chalk of the Crimea is really a tertiary formation, and that the localities on the Dniestr are the only ones which are well ascertained in Russia.

No particulars can be gathered of the eastern or north-eastern boundaries of this formation. We may conjecture, however,

1

that they pass by the Valday hills to the mouths of the Vistula; thence, the northern border must run eastward through the Baltic to the island of Rugen.

CHALK DEPOSITS NOT IMMEDIATELY CONNECTED WITH THE GREAT CENTRAL BASIN OF EUROPE.

(A.) Ireland.

In Ireland, a remarkable deposit of chalk forms the basis of the great basaltic area in the north-east angle of that island; it contains flints; the organic remains agree with those of England; the thickness of the whole deposit does not exceed between 200 and 300 feet; it rests on green sand.

(B.) South-west of France.

Chalk is said to occur on the borders of the tertiary basin of the Garonne, near Dex, on the south-west, and along its northern border. (See the preceding article on green sand.)

(C.) Spain.

In Spain, chalk is said to occur near Cervera, on the road from Barcelona to Lerida; gypsum abounds in the same neighbourhood, and at Pleacente, two miles from Valencia, but the descriptions are too vague to be relied on; the gypsum mentioned seems to be rather that of the red sandstone, than of the formation above the chalk, and possibly a cretaceous marl may have been mistaken for the latter rock.

(D.) Italy.

In Italy, the Scaglia, which covers the extreme secondary chains of the Alps in the Veronese, may perhaps be a variety of chalk; it is described as a calcareous bed, containing nodules and beds of variously coloured flints, resting on the oolites and white limestones, and dipping under the tertiary hills (i. e. those consisting of the formations more recent than the chalk); it reappears against the volcanic group of the Euganean hills near the mouth of the Po, which appear to have forced it upwards.

(E.) Basin of Bohemia, and the Valley of the Elbe.

Dr. Bouè announces that the formation in this district, long known under the name of planer kalk, is really chalk. In the Valley of the Elbe, he has seen scattered patches of it in the bottom of a sinuosity in the granite near Mahles, on the east of Meissen; between Plauen and Strehlad, west of Dresden; at Colditz, and near Zchist, south of Pirna.

In Bohemia, between Toplitz and Bileu, and along the Laun to Lobositz and Grabern, sometimes supporting basaltic cones. More to the south, this deposit appears to have formerly covered the coal and red sandstone formations over an area bounded by two lines, one passing from Hohenmouth to Prague,