Casterton, near Stamford, and in the Essendine and Danes Hill Cutting of the Great Northern Railway.1

The similarity in position of the ferruginous rock, between the Lias and White Oolites, is seen in the Spittlegate Cutting, and to the south of it at Ponton, in the same railway; also in the neighbourhood of Lincoln, where the Lias, which occurs in the Valley of the Witham, is overlain by the ferruginous bed, which, in its turn, is covered by compact white Oolitic limestones, yielding durable stone for building purposes (the "Silver-bed" and Roestone-bed), and containing Mollusca of Inferior Oolite age, as Ceromya Bajociana and other species.

Further north, as well known to Professor Phillips, the ferruginous beds at Brough, on the Humber, containing numerous Rhynchonella spinosa, and other shells, are followed in that area by beds known as the Cave Oolite, which is the equivalent of the limestones of Whitwell and Weston.

Fossils of the Lower White Limestones of Morcot, Stamford, Denton, etc. :

Natica cincta, Phil. Nerinaa cingenda, Phil. N. triplicata, Br. Lucina Wrightii, Op. L. despecta, Phil. Ceromya Bajociana, D'Orb. Pholadomya fidicula, Sow. Hinnites abjectus, Phil. Gervillia Hartmanni? = G. radians, Lyc. Lima Pontonis, Lyc. L. bellula, Lyc. L. cardiiformis, Sow. Macrodon Hirsonensis, D'Arch. Trigonia Phillipsi, Lyc. T. hemispherica, Lyc. Tancredia axiniformis, Phil. Inoceramus obliquus, Lyc. Astarte elegans, Sow. A. minima, Phil. Pecten pumilus, Lam. Cuculloa cancellata, Phil. Ostrea sulcifera, Phil. Goniomya v― scripta, Sow.-Pygaster semisulcatus, Phil. Hyboclypus agariciformis, Forbes. Stomechinus germinans, Phil. Echinus perlatus, Desm. Pseudodiadema depressum, Ag. Echinopsis rotata.-Pecopteris polypodioides, Pterophyllum comptum, Palæozamia pecten.

Fossils of the Collyweston Slates:

Pecten pumilus, Lam. (P. personatus, Ziet.) Avicula elegans, Munst. A. Braamburiensis, Phil. Hinnites velatus, Goldf. Gervillia acuta, Sow. Pinna cuneata, Sow. Modiola Sowerbyana, D'Orb. Astarte excavata, Sow. Trigonia costata, Sow. T. compta, Lyc. Cucullaa cancellata, Ph. Pholadomya fidicula, Sow. Ceromya Bajociana, D'Orb. Cardium Buckmani, Lyc.? Lucina Wrightii, Op. Goniomya literata, Sow. Homomya crassiuscula, Lyc.? Lingula Beanii, Phil. Perna rugosa, Goldf.— Pterocera Bentleyi, Lyc. Alaria Phillipsi, D'Orb.

Brief and imperfect as is this notice, I think that the facts previously stated suggest that the position of certain parts of the Lower Oolites should be reconsidered, and that attention should be drawn to the following points.

1. That the red or ferruginous rock, immediately overlying the Lias, and extending over the district watered by the Nen and the

1 Morris, Quart. Journ. Geol. Soc, ix. p. 330.

2 W. Bedford, Account of the Strata of Lincoln, Mag. Nat. Hist. 1839, p. 653. The Cathedral is built of the "silver-bed" and of the beds below it; the Roestone was used for the construction of Newport Arch, built by the Romans.

Welland, belong, by its fossils, to the Inferior Oolite, and, probably, represents in time part of the "Dogger beds" of Yorkshire.

2. That the Sands and concretionary calcareous Sandstones known as the Collyweston and Wittering slates, as well as a part, if not all, of the overlying Oolite (Ponton, Corby, Stamford, Barnack, Morcot,) also belong, by their fossils, to a higher zone of the Inferior Oolite, and may be the equivalent in time of the beds overlying the Dogger.

3. That the Upper White Limestones and Shales, over certain parts of the area of Northamptonshire, are the representatives of the Great Oolite.

4. That in the Upper and Lower Oolites of Lincolnshire, above the red rock, there are very few Cephalopoda, and that the lower zone is marked by the prevalence of Nerinæa, Astarte, Tancredia, Quenstedtia, Trigonia, Cardium, Cucullæa, Alaria, and a large Natica, associated with fragments of Pterophyllum and other Cycads, and Pecopteris polypodiodes, a species largely represented in the Oolitic Shales of Yorkshire. They have been placed provisionally upon the horizon of the Great Oolite, but their fauna would seem rather to connect them with the Inferior Oolite,' Lycett.

5. That from the general fossil contents of these beds, they present characters intermediate to the more truly marine conditions of the south-western or Gloucestershire area, and the Fluvio-marine and Terrestial deposits of Yorkshire.

6. That the Collyweston slates contain chiefly a molluscan facies, while those at Stonesfield comprise a rich and varied fauna of shells, crustacea, insects, fishes, reptiles, mammals, and many plants.

The following are some of the localities where sections may be observed and fossils obtained, in illustration of the preceding remarks:

1st. Southern Area.-Pits around Blisworth, where the Lias, Red Rock, and Oolites may be seen.

The quarries around Northampton, and northwards at Kingsthorpe, Moulton Road, and at Duston, beyond Dallington.

The pits around Wollaston where the Upper Oolite with T. digona may be seen.

Higham Ferrars, Raunds, Stanwick, and Oundle, (where Ophioderma Griesbachii was found.

The sections near Wellingboro', Kettering, Finedon, etc.

The quarries around Wansford, where Dr. Fitton mentions that the fern referred by Lindley and Hutton to Lonchopteris Mantelli, was found, from which it was inferred that traces of the Wealden occurred in Northampton."

2. Northern Area. The pits around Stamford, Casterton, and Ketton. The quarries at Collyweston and Easton, and further west at Morcot and Luffenham.

Unfortunately the collection made by me, which would have afforded incontrovertible palæontological evidence of the beds in this 1 See a paper by Mr. Horton in the Geologist, vol. iii, p. 249.

2 Fitton, Geol. Trans., vol. iv. p. 309, but corrected at p. 383*, and also in Geol. Jour., vol. xi. p. 337.

district, is now in great measure dispersed, but the re-consideration of the sections made at that time in traversing the district, suggest the position assigned in this paper to the ferruginous Oolite and the Collyweston slates.

Some of these observations, which I now recall with so much pleasure, were made in company with Captain L. L. B. Ibbetson, F.G.S., Mr. J. Bentley, Mr. Samuel Sharp, F.S.A., F.G.S.,1 M. Trigér, and the late Dr. Oppel, who has embodied part of his observations in his great work on the Jura formation.

III. ON THE RELATIONS BETWEEN THE SKIDDAW SLATES AND THE GREEN SLATES AND PORPHYRIES OF THE LAKE-DISTRICT.

By HENRY ALLEYNE NICHOLSON, D.Sc., M.B., F.G.S.

THE Skiddaw Slates, or Lowest Silurian Rocks of the Lake

interbedded traps and porphyries, to which the name of "Green Slates and Porphyries" has been applied, and it has always been believed that the relations between the two were those of perfect conformity. As early, however, as the year 1867 I was led, from certain phenomena which I had observed, to express the opinion that "whether the Green Slates are really conformable with the Skiddaw Slates is a question which admits of doubt, though data are wanting to arrive at a definite conclusion." (Geology of Cumberland and Westmoreland, p. 33.) In the beginning of November, 1868, I discovered what seemed to be a marked want of conformity between the Skiddaw Slates and the Green Slates, the localities where this occurred being the eastern side of the mouth of the vale of St. John, the west side of Derwentwater (near Lowdore), and the mouth of Borrowdale. As these phenomena had not been previously noticed by any former observer, and as they appeared to me to be of considerable importance, I have made a systematic investigation of the subject, and have arrived at the following results.

Beginning with the main area of the Skiddaw Slates, in the north-western portion of the Lake-district, the upward boundary of the slates can be traced to the south of the area from Troutbeck on the north-east to near Egremont on the north-west, a distance of more than twenty-five miles. Along this line the relations between the Skiddaw Slates and the overlying Green Slates are as follows:

In the course of Troutbeck Beck, close to the little village of Troutbeck, the upper, soft, and shaly beds of the Skiddaw Slates are seen on the western side of the stream, dipping S.S.E. at 65°. These are overlaid in the eastern bank of the river, by the basement beds of the Green Slate Series, consisting here of cleaved felspathic ashes, dipping S.S.E. at 50°. About three-quarters of a mile further up the river the upper bed of the Skiddaw Slates are again

1 It is interesting to record that Mr. Sharp has, during many years, collected largely both in the neighbourhood of Stamford and Northampton from these beds, and has thus enlarged our knowledge of the Oolitic fauna of this district.

seen, dipping S.S.E. at 55°, and shortly succeeded by a felspathic trap, the inclination of which could not be determined. Proceeding westwards, no sections are obtainable till Mosedale Beck is reached at a distance of about a mile and a half. Here the shaly, upper beds of the Skiddaw Slates are seen just below the road from Matterdale to Threlkeld, dipping N.N.E. at 55°; and surmounted by the massive trap which forms Wolf Crags. For a short distance to the west of Mosedale Beck the Skiddaw Slates are separated from the lowest trap of the Green Slates by a boss of intrusive felstone derived from the syenite of the vale of St. John. The two shortly come together again, and are seen in a ravine in one of the eastern spurs of Clough Head, where the dip of the Skiddaw Slates is from 45° to 60° to the S.S.E. All along the flanks of Clough Head the upper beds of the Skiddaw Slates can be traced at a considerable elevation, and overlaid by the felspathic trap before-mentioned. In many places they are a good deal disturbed, and are often indurated and penetrated by small veins of quartz, but the dip is mostly to the S.S.E. at angles of from 30° to 50°. In the ravine which leads from Threlkeld Common to Lowthwaite in the vale of St. John, the Skiddaw Slates are seen near the top of the ascent, dipping S.S.E. at 55°. They appear to be continued underneath Wanthwaite Crag, nearly as far as Lowthwaite, the same felspathic trap appearing to rest upon their upturned edges for the whole distance; but this is perhaps due to faulting, as the country is a good deal disturbed, and there is no clear section.

On the opposite side of the vale of St. John (i.e., the western side), an intrusive syenite intervenes between the Skiddaw Slates and Green Slates. There is still, however, evidence of a want of conformity. Thus all along the flanks of Naddle Fell a succession of bedded traps and greenstones, with intercalated thin bands of ashes, is exceedingly well displayed, forming a series of oblique terraces, which dip S.S.E. at about 30°. The angle of dip, therefore, of the lower part of the Green Slate Series is very markedly lower than the dip of the Skiddaw Slates on the opposite side of the valley, and indeed in almost all localities, since this is usually between 45° and 65°. The same low inclination of the Green Slate Series is equally well exhibited in the parallel valley of Naddle Beck, in the northern end of Castlerigg Fell. Between the vale of St. John, however, and the town of Keswick, the upward termination of the Skiddaw Slates is not seen, as the country is thickly covered with drift.

In the bed of the Greta, in Keswick, the Skiddaw Slates are seen dipping southward at high angles, and succeeded to the south by the greenstone of Castle Head, a little wooded hill close to the town. On the western side of Derwentwater the junction between the two formations can be traced about half a mile to the south of Portingscale. Thus the wooded hill, called Fawe Park, is composed of the upper beds of the Skiddaw Slates, dipping S.S.E. at from 40° to 50°. These are succeeded at Rosetrees by a felspathic trap, immediately succeeded to the south by the Skiddaw Slates

again. The trap can be traced along the strike for some two or three hundred yards, but no trace of it appears on the side of Swinside, a little to the west of Rosetrees. These phenomena are caused by the existence of an enormous E.N.E., and W.S.W. fault, whereby almost the whole-if not the whole-of the Skiddaw Slates are repeated to the south of this point. The existence of this fault was determined by me in November, 1868, and I made out at that time that the upper boundary of the Skiddaw Slates, instead of running, as formerly supposed, up the vale of Newlands to the foot of Buttermere, was really to be found some three miles to the south of this line, passing by Lowdore, High Lowdore, Grange, and the Hollows, in a south-west direction towards the head of Buttermere. These facts will be rendered easily intelligible by the accompanying section.1

Fault.

Fig. 1. Section from Portingscale, along the west side of Derwentwater, to Castle Crag in Borrowdale. Length of section five miles.

a. Skiddaw Slates.

6. Felspathic trap, forming the base of the Green Slate Series. c. Cleaved Breccias and felspathic ashes (Green Slates).

Proceeding now to the east side of Derwentwater, the Skiddaw Slates are seen at various points between Lowdore and Grange. They form the lower portion of the ledge over which Watendlath Beck falls to form the celebrated cascade of Lowdore, the upper portion of the ledge being formed by the felspathic trap, which constitutes the base of the Green Slates. They are well exhibited, also, in a field about half way between High Lowdore and the village of Grange. They possess here all their usual character, and dip E.S.E. at 60°. They form a number of ice-worn bosses on both sides of the road, and they are immediately succeeded by a felspathic trap of a dark-green colour, compact, and fine-grained, which forms the northern end of Grange Fell. The dip of this trap could not be accurately determined, but its apparent inclination is small. Crossing to the western side of the valley of Borrowdale, the junction between the Skiddaw Slates and the Green Slate Series is very well seen near a farmhouse called the Hollows, about three-quarters of a mile

The further continuation of the Newland's Valley fault to the east is stopped by a north and south fault which must occupy the line of Borrowdale and Derwentwater. Westwards it appears to be cut off by the great mass of intrusive felstoneporphyry which forms the group of mountains between Buttermere and Ennerdale, and of which Red Pike, High Stile, and High Crag, are amongst the more striking elevations.

S.