Memoir illustrative of a general Geological Map of the principal

Mountain Chains of Europe. By the Rev. W. D. Conybeare,
FRS. &c.

(Continued from p. 16.)
[Some copies of the map having been, in the hasté of publica-
tion, incorrectly coloured, the reader is requested to compare the
colours with the dotted outlines. Where they do not coincide,
the former are erroneous; the errors are generally of a nature
which will admit a ready correction by these means.

It will be
seen that some parts of the present article are taken from a
former publication by the same author.]

Carboniferous Series.
The carboniferous series, considered in the largest acceptation
of the term, comprises, besides the coal measures properly so
called, certain other formations of limestone and sandstone, so
associated with them, that the attempt to separate them would
materially interfere with the clearness of a natural division.

1. The coal measures, properly so called, consist of numerous
alternations of seams of coal with beds of slate clay and sand-
stone.

2. These repose on an alternating system of shale and grit, in which the peculiar limestone characterising the coal districts makes its first appearance in any considerable quantity. The coal seams here become few and unimportant.

3. A system succeeds characterised by the predominance of the limestone called, from its relation to the coal fields, carboniferous. The coal seams in this system are reduced to slight traces which have never yet been worked.

4. A vast deposit of quartzose conglomerate and sandstone, commonly called old red sandstone, forms the lowest formation this

great natural order. No coal has yet been observed in or below this formation.*

6. Trap rocks of various kinds (basalt, greenstone, porphyry, and amygdaloid) occur associated with the preceding formations in various modes of combination, as dykes, irregularly interposed or overlying masses, and sometimes as alternating beds. The phenomena are such as often to render it doubtful whether they are of cotemporaneous origin with the rocks among which they

in

occur ; and in the opinion of many geologists favour the hypo

' thesis of their ignigenous formation.

All these formations are shown in their constant and regular order of succession in the greater part of the English and Irish coal fields; and the only Scotch coal field of which we have any distinct account (that of Clackmannan), entirely harmonises. The structure of the carboniferous districts of the Netherlands, and (if we may judge from Beudant's description), of Hungary also, is exactly parallel. In some instances, however, the third and fourth systems being deficient, the coal measures repose, immediately on the transition limestones, slates, &c. (as in Colebroke Dale, and Dudley, in England; in the Hartz, and many places on the Continent.

The order of superposition, however, is never inverted, nor is there one single instance on record in which

any

workable seam of coal has been found below the third or fourth system above enumerated, unless we consider the anthracite sometimes associated with transition slates, and which may be readily distinguished from the true coal formation, as an exception.

The limestones of the third series, and the conglomerates and sandstones of the fourth, are generally referred by continental geologists to the transition class. (See Von Raumer on the Slate Mountains of the Netherlands, &c. Daubuisson, Geologie; Beudant, Hongrie ; Humboldt, &c.). The representations of every one of the above writers render it absolutely impossible to confound the rothetodteliegende of Germany with the conglomerates of the fourth system above described.

I have, in another work, assigned my reasons at length for constituting a separate crder to include the whole of these four systems rather than referring any part of them to the transition class with which, however, they are very nearly allied.

The geologists of the Continent very commonly consider the rothelodteliegende (a formation immediately overlying the coal measures), as forming part of this series.

I prefer the view entertained by Prof. Buckland, who has, in repeated journeys in the north of Germany, minutely examined the relations of the rotheliegende with reference to this question, and who considers it as the lowest member of the great sandstoneseries forming the next natural group above the carboniferous series. Though conscious how little weight my own evidence will add to this high authority, I may briefly state that my own personalexamination of the Thuringerwald led me to the same conclusion. I have only at present to repeat my assertion, that Lehman, Freisleben,* Von Buch, Von Raumer, Karsten, Keferstein, Daubuis

n

son, and Humboldt, all concur in assigning to the great mass of the rothetodteliegende a position above the coal measures. As that assertion has been questioned, I shall shortly support it by detailed quotations in their own words; and I have only to regret a controversy which renders inevitable a method of proof that must necessarily occupy so many pages usually devoted to much more interesting and valuable matter.

I have thought it necessary thus far to explain the principles on which I proceed in separating the consideration of the rothetodteliegende from the description of the continental coal districts.

A rock placed exactly in the situation of the rotheliegende (that is, between the coal measures and magnesian lime), is specified in Smith's map of Yorkshire, under the name of the Pontefract rock. He classes it with the coal measures; but the course he assigns to it is unconformable to these, and conformable to the superjacent magnesian limestone. This rock ought to be carefully examined and described. It should be observed that as the rocks overlying the coal

cover them unconformably throughout England, instead of succeeding in a regular and conformable series, we have no evidence that the highest beds of the coal formation are

measures

zu trennende formationen,” as two very nearly allied formations, but nevertheless distinct from cach other ; and, conformably with this view, he carefully distinguishes cer. tain coal seams which, according to him, actually are subordinate to the rotheliegende from the true coal formation. " My observations," he states, “ lead to the conclusion, that a part of the beds hitherto referred to the coal formation (properly so called) ought to be separated from that formation, and regarded as subordinate to the rotheliegende.

Ein theil der bisher zu den eigentlichen Steinkohlen gebirgen gerechneten Steinkohlen flosse von solchen abzusondern, und dem rothlicgenden unterzuordnen ist.” Mr. Weayer has suffered himself to be misled by neglecting to advert to the circumstance, that the passages he has quoted from Freisleben, as proving that the coal formation generally is included in the rotheliegende, have no kind of reference to the “ eigentlichen Steinkohlengebirgen,” the proper coal formation, but are confined to that part of the series thus carefully separated from it by that author on account of this very position. The cause that seems to have led to this misconception is, that the two formations being conterminous, the true coal formation, and these subordinate beds, often occur nearly in the same localities. A careful collation of the map accompanying Freisleben's work with his text removes in the most convincing manner this source of confusion.

The plan of Freisleben's work does not extend to the coal formation properly so called. I should add that the passages above cited from Freisleben are not incidental notices ; but form the express declaration of his opinion on this point deliberately pronounced in the section dedicated to the consideration of the relations to which they refer.

I refer to the account of the environs of Glatz by Von Buch for his testimony in this controversy. Dr. Anderson's notes in this translation of that work will convince Mr. Weaver that I am not singular (as he appears to suppose) in my interpretation of Freis leben's sentiments, but have the authority of those best versed in the geological writings of Germany.

Freisleben cites from an author (Karsten) who classes the coal and rotheliegende togea ther as subordinate members of one great sandstone formation, the following enumera, tion of the several beds included by him in that formation, taken in an ascending order. 1. Conglomerate of ancient rocks. 2. Siliceous conglomerate. 3 to 8. Coal sandstone and shale. 9. Trap rocks. 10, Clay jronstone. 11. Rotheliegende. 12. Weiss liegende. Now if we look among these rocks for the representative of our own old red sandstone, it must be sought in Numbers 1 and 2, not in Number 11.

in any part of the island displayed, inasmuch as all the beds of
that formation come indifferently into contact with the super-
strata. It is possible that were those highest beds visible, they
might be found to exhibit a gradual transition (as is the case in
so many other instances) into the characters of the next sandstone
series. If we are to refer the rotheliegende to the coal forma-
tion in any manner, it can only be in considering it as thus inter-
mediate in place and character between the regular coal mea-
sures and the sandstones of the next æra. To identify it in any
way with the lowest beds of the whole system is to invert every foun-
dation of geological arrangement, and to unseitle all those princi-
ples to which the science owes its present precision.
DISTRIBUTION OF THE CARBONIFEROUS Series.

(A.) Coasts of the Baltic.
Following the same course which was pursued in indicating
the distribution of the ancient chains, we may first trace the
coal formation, where it appears to rest against the most north-
erly of these chains, that of Scandinavia.

În this line, we find coal in the island of Bornholm, and again in Sweden on the south of the primitive tract near Helsingborg, at the mouth of the Baltic.

(B.) Scotland. If we regard the Grampian mountains as a prolongation of the Scandinavian chains, the great coal district of Scotland must also be considered as similarly related to those above-mentioned. It occupies the tract forming what may be called the great central valley of Scotland (speaking relatively, for considered in itself its surface is very considerably varied), which lies between the great transition chain on the south, and the still loftier primitiye ranges of the highlands on the north. The whole of this wide tract is occupied by the coal measures, the carboniferous limestone, and the old red sandstone, associated in every possible manner with vast accumulations of every variety of trap.

In the low district on the east of Sutherland, where the secondary formations again intrude among

the primitive highland chains, coal has been discovered at Brora; but from the slight description incidentally given of this tract in the memoir of Mr. Bald" (vol. iii. Trans. Wern. Soc.), before referred to, it may be conjectured that this does not belong to the principal coal formation, but to those beds which occasionally occur in more recent formations, being, perhaps, of the same æra with the coal of the Cleaveland district in Yorkshire,

In Dumfrieshire, near the southern or transition chain of Scotland, we find many limited coal-fields reposing against, or . forming narrow basins in, the valleys of the latter chain; these are associated with, and rest upon as usual, thick beds of the carboniferous limestone.

Trap rocks (porphyry, greenstone, basalt, &c.),occur extensively associated with and overlying the coal districts of Scotland.

(C.) Ireland. We shall next proceed to Ireland, postponing the enumeration for the present of the English coal districts; because the former country is more immediately connected in its geological relations with Scotland.

As we have already traced the primitive and transition chains from the south-west of Scotland to the north-east of Ireland, the formations of the great central valley of Scotland here likewise intervene, and among them the coal measures, which may be seen emerging from beneath the overlying basalt at Fairhead on the north-east, and again just beyond the south-west of the basaltic area at Coal Island and Duncannon; but other parts of Ireland present far more important coal districts. Indeed the island may generally be described (with the exception of the north-east basaltic area) as being almost surrounded with a series, of primitive and transition groups, including a great central area entirely occupied by the old red sandstone, carboniferous lime, and coal measures. The structure of these districts very closely corresponds with the tracts of the same formation in England.

The coal district already mentioned is termed by Mr. Griffiths: the, Ulster coal district. There are three other principal coal fields.

2. The Connaught coal district occupies an extensive tract, in the centre of which Lough Allen is placed..

3. The Leinster coal district is situated in the counties of Kilkenny, Queen's county, and county of Carlow. It also extends a short distance into the county of Tipperary, as far as Killenaule. This is the principal carbonaceous coal district. It is divided into three detached parts, separated from each other by the carboniferous limestone, which not only envelopes, but in continuation passes under, the whole of the coal district.

4. The Munster coal district occupies a considerable portion of the counties of Limerick and Kerry, and a large part of the county of Cork. It is by much the most extensive in Ireland but as yet there is not sufficient information respecting the number, extent, or thickness, of the beds of coal it may contain.

(D.) England. The coal fields of England will, from geographical position, naturally fall under the following arrangement: 1: The great northern district, including all the coal fields north of Trent. 2. The central district, including Leicester, Warwick, Stafford, and Shropshire. 3. The Western district, which may be subdi vided into North-western, including North Wales, and the South western, including South Wales, Gloucester, and Somersetshire.

this