Figure III. is a section drawn from the north-western corner of the Coalfield at Denholme, through Batley, Wakefield, Hemsworth, Doncaster and past Gainsborough.

The faults are not shown on the section, but the dip is averaged from the outcrop to the deepest point. The writer thinks it quite reasonable to omit the faults from this section because he has observed that in this Coalfield a seam of coal descends from the outcrop to the deepest place where it has been proved sometimes by a general dip and sometimes in steps. These steps are the faults, but for the purpose of a general section such as this it does not matter whether the dip is shown as proceeding along a slope or whether the detail of the steps or faults is shown.

One of the most interesting questions is that of the level of the upper surface of the Carboniferous formation where this formation is covered up by the Permian. In the section the present average inclination of the Carboniferous land surface is shown having a gentle dip from west to east. Another dotted line shows the possible inclination of the Carboniferous land surface before the Permian was deposited and the denudation of the Coalfield was completed down to its present level. If that inclination should continue there must be an enormous thickness of more recent formations. It is, however, possible and probable that the easterly dip of the ancient surface is less rapid, and it is possible that there may be a ridge of the Carboniferous formation under Gainsborough. That the inclination of the old land surface flattens appears to be now proved by the boring near Haxey.

The total thickness of the Yorkshire Coal Measures has not yet been definitely ascertained. It may be that east of the Permian outcrop the dip of the Coal Measures may in some places be steeper than the dip of the l'ermian, in which case there will be room for a greater thickness of Coal Measures above the Barnsley bed than has yet been proved. It is believed that the section line No. III. is taken along the deepest or one of the deepest troughs of the Coalfield.

At Deholme there is the greatest westerly extension; along the northern outcrop of the Coalfield there is a southerly dip, for instance,

at the now closed Newton Colliery, near the northern outcrop, the Warren House coal, which corresponds to the Barnsley bed, lies about 500 feet below the sea level, giving a dip of 1,300 feet in ten miles from north to south. Going further south, the coal rises from South Kirby to Denaby Main, where, on the corresponding line of longitude, this coal is only 1,200 feet in depth. It is, therefore, evident that South Kirby is very nearly in the centre of a trough from which the coal rises north and south and west. There will also be from South Kirby a gradual eastwardly dip.

The deepest shaft yet sunk to the Barnsley bed is that at Cadeby, about four and a-half miles south-west of Doncaster, where the coal is 750 yards deep. Judging from the rate of inclination down to the east, proved by the dip of the coal from the outcrop near Barnsley to Cadeby, it is probable that the depth under Doncaster will be about 1000 to the Barnsley bed, and it may be a little more and it may be a little less.

The total thickness of the Yorkshire Coalfield yet proved down to the Millstone Grit is about 4,700 feet, or in round figures 5,000 feet. There are altogether about fifty seams of coal, and the total thickness is over 100 feet.

seam.

In

At the present time coal seams are worked in Yorkshire varying in thickness from about 14 inches to 10 feet. A 14-inch coal can only be profitably worked under peculiar local conditions, and it is only in a few localities that 10 feet of coal are found workable in one In Yorkshire any coal under 3 feet is classed as a thin seam. The Coalfield is roughly divided into two districts by a line of longitude passing through Leeds. Westward of this line of longitude is the thin coal district and eastward is the thick coal district. the thin coal district the coal is got in the proximity of the town and factory where it is used, though the working cost is pretty high, amounting to 7s. or 8s. a ton. In the district to the east the coal seams are 3 feet and upwards and the cost of working is greatly reduced, but the larger collieries have to send most of their coal some distance by railway or canal. Before this Coalfield is exhausted every seam of coal over 4 inches in thickness will be worked, and in

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many districts, where thick coals have been worked and exhausted, the old wastes will be worked over again for the sake of the slack, the pillars, and beds of inferior coal that have not been considered good enough for the market. When this time comes the average price of coal at the pit top will be perhaps 20s. a ton, and the smoke nuisance will be considerably abated.

THE OCCURRENCE OF LIMESTONE CONGLOMERATES ON THE NORTH SIDE

OF THE CRAVEN FAULTS. BY R. H. TIDDEMAN, M.A., F.G.S., OF H.M. GEOLOGICAL SURVEY.

(Read November 7th, 1894.)

(Communicated with the permission of the Director General of the Geological Surveys of the United Kingdom.)

In 1890, when the British Association met at Leeds, at the request of the Local Committee I drew up a description of the "Physical History of the Carboniferous Rocks of Upper Airedale," which appeared in the Local Handbook presented to the visitors. Through the instrumentality of your late Secretary, Mr. Jas. W. Davis, this paper was rescued from the limbo of so ephemeral a publication, and printed in the Proceedings of your Society (vol. xi. part iii).

Amongst other things it called attention to the great discrepancies in the Lower Carboniferous Rocks on either side of the Craven Faults, and showed that these different types, which were called the Bowland and Yoredale types, extended, the one from the plains in Lancashire bordering the Irish Sea to the Craven Faults, and the other from those faults away to the Scottish border. It was pointed out that these two distinct types showed no tendency to assimilate at the line of junction, but were if anything still more pronounced there.

The enormous thickness of the rocks on the Bowland, south, or downthrow side of the faults (as compared with the Northern or Yoredale type) was regarded as evidence that the faulting was going on concurrently with the growth of the deposits on that side.*

Further, an attempt was made to sketch out the geography of the Carboniferous seas in the North of England at that early period. A moderately full description was given of the "Knowl Reefs" of the country on the south side of the Craven Faults. These are great mounds of white limestone made up of organic remains, such as Brachiopods, Lamellibranchs, Gasteropods, Crinoids, and Corals.

See also paper by the author, "On Concurrent Faulting and Deposit in Carboniferous Times in Craven, Yorkshire, with a note on Carboniferous Keefs. Tran. Brit. Assoc., Newcastle-upon-Tyne, 1889.

Evidence pointed to their having grown up as reefs on a slowly sinking bottom by the growth and death of the animals of whose remains they are formed. It was shown that they were formed in shallow seas, and that the tops of them were often awash in the turmoil of the waves. In short they formed islands or reefs. One of the points of evidence was the frequent occurrence on their sides or on the seabottoms surrounding them of angular fragments of the limestone, which had evidently been broken off from them in the surge of the sea, and had either accumulated on their sides at an angle of rest or had been consigned to the deeper water below, and subsequently covered up by the shale and mud of a later stage. These so-called breccias were generally made of angular fragments, but occasionally the pieces were well rolled into pebbles, and the deposit might be called a conglomerate.

In summing up the bearing of these and kindred facts on the geography of these Carboniferous Seas I wrote as follows:-"If we ascend to the top of the crags above Malham Cove we soon find ourselves upon the great plateau of the Mountain Limestone proper. This, though broken at the foot of Malham Tarn by the North Craven Fault which throws up the base and shows us how thin it is, and crossed by many minor faults, is one and the same as the great spread of Mountain Limestone which lies beneath all the Yorkshire Dales, and extends north beyond the Tyne Valley. We have crossed the Fault and in so doing have exchanged the Clitheroe or Bolland series for the Yoredale type, and if we could realize the state of affairs when these rocks were forming we should probably say that we had left a deep sea dotted with islands and come on to a wide and long and shallow reef." The sea with the islands was a generalization, the result of a very fair amount of evidence. The long reef was hardly more than a conviction based on probabilities. Some evidence I had seen, but hardly enough to form a satisfactory demonstration, and at first sight it seemed unlikely that any remains of the beach of that supposed reef, ranging along the flanks of the high hills which border on the Craven Faults, would be present, if it had ever existed.

It was, therefore, a pleasant surprise when I was working in the