TRANSACTIONS OF SECTION C.

they have not (Kentish Town, Crossness, Richmond, Streatham, and Culford), and it is in the latter group too that the character of the beds leaves their age in doubt. So far another must be added to these, as no fossil has yet been found in the old rocks at Stutton.

Of the above 10 deep borings in the London Basin (using that term in the widest sense, as including the Chalk tract that everywhere surrounds the Tertiary beds) we owe 9 to endeavours to get water from deep-seated rocks, and in addition to these 9 we have several other deep borings, which though not carried through to the base of the Secondary rocks, yet give us much information concerning those beds (at Holkham, Norwich, Combs, Winkfield, London, Loughton, Chatham, and Dover). In one case only, that of Dover, has the work been done for the purpose of exploration, but now, after a few years' interval, a second trial has been made at Stutton.

Now both of these borings were started for a much more definite object than merely to prove the depth to older rocks, or the thickness of the Cretaceous and Jurassic Series. There is one particular division of those older rocks that has a distinct fascination for others than geologists. We, happily, are content to find anything and to increase our knowledge in any direction, but naturally those who like to find something of immediate are not geologists, as well as many who are, practical value. As already shown, we owe much knowledge of the underground extension of formations to explorations for water; it has now become the turn of geologists to help those who would like to find that much less general, though nearly as needful and certainly more valuable thing, coal.

The first place to suggest itself to those geologists who had worked at this question, as a good site for trial, was the neighbourhood of Dover, and for various The trial has been made, and successfully, several hundred feet good reasons. of Coal Measures having been found, without reaching their base, but with several beds of workable coal.

Beyond that neighbourhood, however, geologists are not in such accord, and generally speaking, fairly good reasons can be given both for and against the selection of many tracts for trial, except in and near London, where no geologists would recommend it, from the evidence in our hands.

Let us then shortly review the evidence that we have on the underground extension of the older rocks in South-Eastern England, with a view of considering the question of the possibility of finding Coal Measures in any of the folds into which those rocks have probably, nay almost certainly, been thrown.

The area within which the borings that reach older rocks in the London Basin is enclosed is an irregular pentagon, from near Dover, on the south-east, to Richmond on the west, thence to Ware, thence to Culford on the north, thence to Harwich, and thence southward to Dover, the greatest distance between any borings being from Dover to Culford, about eighty-six miles. It is therefore over a large tract, extending of course beyond the boundaries sketched above, that we have good reason to infer that older rocks are within reasonable distance of the surface, rarely as much as 1,600 feet, and mostly a good deal less.

We must now consider some evidence outside the tract hitherto dealt with. Southward of the central and eastern parts of the London Basin we have evidence that the Lower Cretaceous beds thicken greatly, from what is seen over their broad outcrop between the North and South Downs. We know also, from the Dover and Chatham borings, that the Upper and Middle Jurassic beds come in to the south-east, whilst the Sub-Wealden Exploration, near Battle, proves that those divisions thicken greatly southward, the latter not having been bottomed at the depth of over 1,900 feet, at that trial-boring.

Westward, however, near Burford in Oxfordshire, and some miles northward of the nearest part of the London Basin, Carboniferous rocks have been found at the depth of about 1,180 feet, these being separated from the thick Jurassic beds (including therein the Liassic and Rhætic) by perhaps 420 of Trias. They consist of Coal Measures, which were pierced to the depth of about 230 feet.

In and near Northampton, north-eastward of the last site, and still further from the northern edge of the London Basin, the like occurs; but the beds found

are older than the Coal Measures, and the Trias is thin, not reaching indeed to 90 feet in thickness, and being absent in one case. At one place, too, the Carboniferous beds have been pierced through, with a thickness of only 222 feet, when Old Red Sandstone was found, and in another place still older rock seems to have been found next beneath the Trias. The depth to the rocks older than the Trias, where they were reached, was 677, 738, and 790 feet, or respectively 395, 460, and 316 below sea-level. Some of these figures must be taken as somewhat approximate, though they are near enough to the truth for practical purposes.

A boring at Bletchley, to the south, reached granitic rocks at the depths of 378 and 401 feet; but these rocks seem to be only boulders in a Jurassic clay: their occurrence, however, is suggestive of the presence of older rocks at the surface no great way off, in Middle Jurassic times.

Much further northward, at Scarle, south-west of Lincoln, the older rocks have been reached at the depth of about 1,500 feet, all but 141 of which are Trias, and they begin with the Permian (which crops out some eighteen miles westward), the Carboniferous occurring after another 400 feet, and having been pierced

to 130.

We have then evidence that over a large part of South-Eastern England, reaching northward and westward of the London Basin, though the older rocks are hidden by a thick mantle of Jurassic, Cretaceous, and Tertiary beds, yet they seem to be rarely at a depth that would be called very great by the coalminer. They are distinctly within workable depths wherever they have been reached.

There is no area of old rocks at the surface in our island, south of the Forth, in which Coal Measures are not a constituent formation. Truly, further north, in the great tract of Central and Northern Scotland there are no Carboniferous rocks; but we can hardly say that none ever occurred, at all events in the more southern parts. We know, though, that on the west and north Jurassic and Triassic beds rest on formations older than the Carboniferous.

It is not, however, to this more northern and distant tract that we should look for analogy to our underground plain of old rocks; rather should we look to more southern parts, to Wales and to Central and Northern England, where Coal Measures are of frequent occurrence. On the principle of reasoning from the known to the unknown, I cannot see why we should expect anything but a like occurrence of Coal Measures, in detached basins, in our vast underground tract of old rocks.

What, then, is the evident conclusion from what we know and from what we may reasonably infer? Surely that trials should be made to see if such hidden coal-basins can be found.

One trial has been made, and it has succeeded; the Dover boring has proved the presence of coal underground in Eastern Kent, along the line between the coal-fields of South Wales and of Bristol on the west, and those of Northern France and of Belgium on the east.

The long gap between the distant outcrops of the Coal Measures near Bristol and Calais has been lessened very slightly by the working of coal under the Triassic and Jurassic beds near the former place, but much more by our brethren across the narrow sea, the extent of the Coal Measures beneath the Jurassic and Cretaceous beds, having not only been proved by the French and the Belgians along their borders, but the coal having been largely worked. At last, we too have still further decreased the gap, by the Dover boring, a work that I trust is to be followed by other work along the same line.

But is this the only line along which we are to search? Are we to conclude that the only coal-fields under our great tract of Cretaceous beds (where these are either at the surface or covered by Tertiary beds) are in Kent, Surrey, and other counties to the west ? Have we no coal-fields but those of Bristol and of South Wales? The bounds of our midland and northern coal-fields have been extended by exploration beneath the New Red Series; are we to stop here and to assume that there can be no further underground extension of the Coal Measures south

eastward? This seems hardly a wise course, and is certainly a very unenterprising one. It seems to me rather that the right thing to be done is to try to find out the real state of things, by means of borings.

There are of course objectors in this as in other matters. Some may say that it is silly to try in Suffolk, and that Essex gives a better chance of success. Others again may prefer Norfolk. And yet others may argue that there is no chance of finding Coal Measures in any of those three counties. But I must confess my inability to understand this line of reasoning; the fact is that the data we have are few and far between, and that we want more. It is really of little use to bandy words, and I do not now mean to take up the matter in detail. We cannot get at the truth except by actual work; justification by faith will not hold in this case, still less justification by unfaith.

Let us hark back a little and call to mind what has happened in the past. I remember the time when certain geologists disbelieved in the possibility of the occurrence of Coal Measures anywhere in South-Eastern England, it being argued that the formation thinned out before it could get so far eastward. Then this view was somewhat varied, and it was inferred, from certain observed facts, that even if Coal Measures did reach underground into these benighted parts, they would be without workable coal, and so practically useless.

Now for some years nothing occurred to upset the prophets of evil, that is to say, no fact came to light. There were not wanting inferences to the contrary, but it remained practically a matter of opinion. One day, however, the needful fact came, and the first boring made specially to test the question (at Dover) disproved both the above negative theories by finding Coal Measures with workable coal. Let us hope that a like result may happen in East Anglia, and that the pessimists may again be in the wrong.

We should not, however, fall into the opposite error, that of optimism. We inust not expect an immediate success like that at Dover. We are here much further from any known coal-field. Advertisements of various wares sometimes tell us that one trial will suffice,' but it is not so in this case. We should not be content until many borings have been made, and we should not be despondent if, after sites have been selected to the best of our judgment, we begin with a set of borings that are unsuccessful in finding coal.

At the time of writing I cannot say that the Stutton boring is a success or a failure as far as coal is concerned, but I am quite ready to accept the latter without being discouraged. Whatever it is you may know during our meeting; it is certainly a success in the matter of reaching the old rocks at a depth of less than 1000 feet. We should remember that every boring is almost certain to give us some knowledge that may help in future work.

There is a further point, however, to be taken into account. A boring that may at first seem to be a failure, from striking beds older than the Coal Measures, may some day turn out otherwise. The coal-field along the borders of France and Belgium is sometimes affected by powerful and peculiar disturbances, by faults of comparatively gentle inclination (far removed from the usual more or less vertical displacements) which have thrown Coal Measures beneath older beds in large tracts. This is no mere theory, though advanced as such at first by some Continental geologists, who have had the great satisfaction of seeing their theory adopted by practical men, and proved to be true, much coal being worked below the older beds that have been pushed above the Coal Measures by the overthrust faults.

Our trial-work, of course, does not yet lead us to consider such disturbances as those alluded to. We have at first to assume a normal succession of formations, and not to carry on explorations in beds that can be proved to be older than the Coal Measures; but the time may come when it will be otherwise.

Another matter to which attention has been drawn by our foreign friends is an apparent general persistence of disturbances along certain lines, or in other words, the recurrence of disturbances in newer beds in those parts where earlier movements had affected older beds; so that, reasoning backward, where we see marked signs of disturbance for long distances in beds at or near the

1895.

X X

surface, there we may expect to find pre-existing disturbances of the older beds beneath. This, however, is a somewhat controversial question, and much remains to be done on it; but should it be proved as a general rule it may have much effect on our underground coal.

Finally, the question of the possibility of finding and of working coal in various parts of South-Eastern England is not merely of local interest; it is of national importance. The time must come when the coal-fields that we have worked for years will be more or less exhausted, and we ought certainly to look out ahead for others, so as to be ready for the lessening yield of those that have served us so well. It is on our coal that our national prosperity largely, one may say chiefly, depends, and, as far as we can see, will depend. Let us not neglect any of the bounteous gifts of nature, but let us show rather that we are ready to search for the treasures that may be hidden under our feet, and the finding of which will result in the continued welfare of our native land.

APPENDIX.

List of the Chief Papers on the Old Rocks Underground in South-Eastern England since 1889, when the literature of the subject was treated of in the Memoir on the Geology of London, &c.

Bertrand, Professor M. Sur le Raccordement des Bassins houillers du Nord de la France et du Sud de l'Angleterre. Annales des Mines and Trans. Fed. Inst. Mia. Eng., vol. v. (1893).

Brady, F. Dover Coal Boring. Observations on the Correlation of the FrancoBelgian, Dover and Somerset Coal Fields, 8vo. 1892. Second Issue, with Additions, 1893. Notice by E. Lorieux in Annales des Mines, 1892.

Dawkins, Professor W. B. The Discovery of Coal near Dover, Nature, vol. 41, pp. 418, 419; Iron and Coal Trades Gazette; Contemporary Review, vol. Ivii., pp. 470-478. The Search for Coal in the South of England, Proc. Roy. Inst. (nine pages); Nature, vol. 42, pp. 319-322. The Discovery of Coal Measures near Dover, Trans. Manchester Geol. Soc., vol. xx., pp. 502-517 (1890).

The Further Discovery of Coal at Dover and its Bearing on the Coal Question. Trans. Manchester Geol. Soc., vol. xxi., pp. 456–474 (1892).

On the South-Eastern Coalfield at Dover, Trans. Manchester Geol. Soc., vol. xxii., pp. 488-510; The Probable Range of the Coal-Measures in Southern England, Trans. Fed. Inst. Min. Eng., vol. vii., 13 pages and plate (1894).

Harrison, W. J. On the Search for Coal in the South-East of England; with Special Reference to the Probability of the Existence of a Coal-field beneath Essex, 28 pages and plate. 8vo. Birmingham (1894).

Irving, Rev. Dr. A. The Question of Workable Coal Measures beneath Essex. Herts and Essex Observer, July 14, 1894.

Martin, E. A. On the Underground Geology of London. Science Gossip, no. 335, pp. 251-254; no. 337, pp. 11-15 (1892, 1893).

Rücker, Professor A. W., and Professor T. E. Thorpe. Magnetic Survey of the British Isles, Phil Trans., vol. 181, see pp. 280 &c., and plate 14 (1891); A popular account by Professor Rücker under the title Underground Mountains, Good Words, January to March 1890.

Topley, W. Coal in Kent. Trans. Fed. Inst. Min. Eng., vol. i., pp. 376-387 (1892).

Whitaker, W. Coal in the South East of England, Journ. Soc. Arts., vol. xxxviii., pp. 543-557; Suggestions on Sites for Coal-search in the South-East of England, Geol. Mag., dec. iii., vol. vii., pp. 514-516 (1890).

Whitaker, W., and A. J. Jukes-Browne. On Deep Borings at Culford and Winkfield, with Notes on those at Ware and Cheshunt. Quart. Journ. Geol. Soc., vol. 1., pp. 488-514 (1894).

The Eastern Counties' Coal Boring and Development Syndicate . . . Geological Reports by T. V. Holmes, J. E. Taylor and W. Whitaker, 15 pages, 8vo. Ipswich (1893). Partly reprinted in Essex Naturalist.

Omitted from Notice in 1889.

Drew, F. Is there Coal under London? Science for All, vol. v. pp. 324–328. Firket, A. Sur l'Extension en Angleterre du Bassin houiller Franco-Belge. Belg., t. x. Bulletin, pp. xcii-xciv (1883).

Ann. Soc. Géol.
Taylor, W.
pp. ii., 22, 8vo.
Topley, W.

On the Probability of Finding Coal in the South-East of England,
Reigate (1886).

On the Correspondence between some Areas of Apparent Upheaval and the Thickening of Subjacent Beds. Quart. Journ. Geol. Soc., vol. xxx. see pp. 186, 190-195 (1874). See also Memoir 'The Geology of the Weald,' pp. 241, 242, pl. vi. (1875).

The following Papers were read:

1. The Southern Character of the Molluscan Fauna of the Coralline Crag tested by an analysis of its characteristic and abundant species. By F. W. HARMER, F.G.S.

Out of 436 species of Mollusca from the Coralline Crag, excluding varieties given in Mr. Searles Wood's monograph, nearly 90 are represented by unique specimens only, and more than 100 others are very rare. Some of these rarer forms may be only locally so, although, with few exceptions, all the species which are common in the Belgian Pliocene beds, of similar age to the Coralline Crag, are common also in that deposit. An analysis of all the shells in any horizon of the Crag in which the same value is attached to forms which are exceedingly rare, and to those which occur in countless profusion, is apt to be, to some extent, misleading. The Southern character of the fauna of the Coralline Crag, and its close resemblance to that of the Mediterranean, is much more strongly evidenced when we confine our enquiry to the more abundant shells of this deposit.

Omitting the rare species, we have 240 which may be regarded as characteristic forms. Of these 89, or about 37 per cent., are regarded by Mr. Wood as extinct, and eight others may be, for our present purpose, taken as such, as they have ceased to exist in European seas, and are only found in parts of the world more or less distant. Of the 143 species remaining, there is only one, Buccinum (Buccinopsis) Dalei, which is not now found living, either in the Mediterranean or the West European area, which Dr. Gwyn Jeffreys said cannot be regarded as zoologically distinct from it. This shell cannot, however, be looked on as a boreal species, as it is given by M. Dollfus as occurring in the Miocene beds of Touraine. Thirty-three of the extinct shells of the Coralline Crag are also found in the Mediterranean Pliocene, either at Monte Mario, or Biot, near Antibes. Altogether 170 species out of 396 found at Monte Mario are common to that deposit and to the Coralline Crag, a larger proportion than is the case with the Diestien beds of Belgium. The practical identity thus shown between the Molluscan fauna of the Coralline Crag, and that of the Mediterranean and West European province, and the close resemblance between both of them and some of the Italian Pliocenes, point to a more direct and open communication between the Mediterranean and the seas of Great Britain at some period subsequent to the coming into existence of the present fauna than exists at present.

The distinctly Southern character of the Mollusca of the Coralline Crag is evidenced by the comparatively small proportion of the species which range northwards into British waters, and this also comes out more strongly when we confine ourselves to its more abundant forms. While there is only one which is British, and not Southern, there are 42, or 29 per cent., of the European species which are Southern and not British. There are, however, nine shells which are characteristic Mediterranean species, and are only included in lists of the British Mollusca because of the occasional discovery of some rare specimen on our coasts. If we regard these nine species as Mediterranean, it raises the proportion of exclusively Southern forms to 36 per cent. The abundant shells are practically all Southern, and if it were possible to count shells, and not species, we should meet