EXCURSION TO THE BERWYNS. had travelled from the coast to do so and had to return that evening. Mr. Wilson, having expressed his great pleasure in meeting the Association, the party then proceeded to Lower Halling, which was reached in good time for tea, which was served in an admirable manner, amid pleasant surroundings, by Mrs. Brigden at the Manor H ouse. After the usual votes of thank s, the members left Halling by the 7.5 I p.m. train for home. EXCURSION TO THE BERWYNS. JULY 31ST TO AUGUST 7TH (LONG EXCURSION), 1908. Director: J. LOMAS, A.R.C.S., F.G.S. Excursion Secretary : H. KIDNER. (R,po,.t by THE D I?ECTOR.) A PATHETIC interest att aches to the publication of the following account as it was completed by Mr. Lomas only a few weeks before his untimely death. Those who took part in the Berwyn Excursion will long remember it as one of the most pleasant and instru ctive that the Association has carried out, and not a little of the pleasure was due to the good temper and kindliness, the energy and enthusiasm, of the Leader, who had sacrificed no small fraction of his holiday in order to conduct the excursion. Mr. Lomas had arranged to visit Algiers in the Christmas Vacation in order to investigate there certain phenomena which promised to throw some new light on a subject always of great interest to him--the origin of the British Trias. He had been appointed Secretary of a British Association Committee charged with this work, and was making his way to Biskra when an unfortunate accid ent happened to the train by which he travelled, resulting in his sad death. It was just before his departure for Algiers that he revised the proof of this account of the Long Excursion of 1908. W. W. WATTS. The official party arrived at Oswestry on the evening of July 30th, travelling from Puddington (G.W.R.) by the 2. I 5 p.m. train. Including some who joined later, about 50 members took part in the excursions. The headquarters were at the "Wynnstay Arms " Hotel, Oswestry, but owing to lack of accommodation some of the members were put up at the" Queen's Hotel," Oswestry, and at other places in the town. EXCURSION TO THE BERWYNS. 49 Friday, july 3ISt.-An early start was made for Llangollen, leaving Oswestry (G.W.R.) at 8 a.m., and this gave an oppor­ tunity to visit Plas Newydd and other places of interest in Llangollen before commencing the geological work planned for the day. Assembling on the Dee Bridge at 10 a.m., the party walked to Pentre-felin, about Ii miles west of the town. In a small quarry by the roadside a considerable number of fossils were collected, including Cardiola interrupta, crinoid stems and graptolites, but their state of preservation did not in all cases admit of precise determination. A discussion took place in the quarry on the stratigraphical horizon of the beds. Situated in the centre of a great syncline of Silurian rocks extending from Glyn Ceiriog on the south to Cyrn-y-Brain on the north, they presumably occupy a high position in the Silurian series, and the faunal contents as far as they could be made out were consistent with the view that the slates are of Ludlow age. On ascending the hill towards the Eglwyseg Escarpment, other exposures of slate were traced until the faulted junction between the Silurian and Carboniferous was crossed near Dinbren Dchaf. The Basement Conglomerates and Sandstones of the Carbon­ iferous series were examined in a roadside cutting near the farm of Dinbren Uchaf and then an ascent was made of the great escarpment. The Lower Brown Limestone crops out in numerous cliff projections from the screes and was found to contain large quantities of the characteristic fossil Daviesiella (productus) llangollensis. Above this a great scar of white limestone succeeds, the top of which marks the limits of the lower and upper parts of the Dibunophyllum-zone (D, andDs- ). The party stopped for luncheon on the dividing line between the two sub-zones, and advantage was taken of the extensive view which the eminence affords to become acquainted with the general features of the landscape. On the east stretches the Triassic plain of Cheshire, its low and level surface broken only by the Keuper escarpments of Beeston and Peckforton. To the south the conical hill of Castell Dinas Bran is separated from our standpoint on the escarpment by a narrow gorge 600 ft. deep, while beyond the castle we view the long line of Silurian hills which form the northerly rim of the Berwyns. Turning towards the west the River Dee winds like a ribbon through steep and wooded slopes, and on the western horizon the Arenigs fill in the notch of the valley. Towards the north-west the Ordovician rocks of Cyrn-y-Brain form lofty hills approaching 1,900 ft. in height, and at their foot the Eglwyseg River, rising in the World's End, has cut a deep gorge. Towards the south-east, and about three miles distant, the limestone quarries of Fron-y-Cysyllte are seen, and as a measure PROC. GEOL. Assoc., VOL. XXI, PART I, 1909.J 4 50 EXCURSION TO THE BERWYNS. of the rapid thinning of the Carboniferous towards the south we note that 600 ft. of the lower limestones beneath our feet are not represented on the opposing slopes across the valley. From our coign of vantage the glacial features of the district can be seen with remarkable facility. We can follow the track of the Dee Valley glacier all the way from its origin in the Arenigs to its termination in the Eastern plain. Its course is marked by a valley within a valley. One, the pre-Glacial, slopes gently from the hills, the other forms a U-shaped notch in the lower part. Across the mouth of the valley where the Dee enters the plain, the great ice stream from the north flowed, and a lofty moraine is now to be seen near the railway viaduct which spans the valley. After lunch the party continued in an easterly course along the escarpment, and as the limestone dips in the same direction newer beds came within the range of observation. At last the limestone gave place gradually to more arenaceous varieties and .). the contained fossils were distinctive of a higher zone (D 3 A descent was now made down one of the ravines to the massive white limestone, and the extensive quarries formerly worked along the face of the Trevor rocks gave good oppor­ tunities for fossil collecting. At one place the limestone was interrupted for a distance of several yards and the space was filled with a curious mass of clay and shaly fragments. The shales were in small, flat, oval or rounded pieces about i inch in diameter, and were of a green or reddish colour. Considerable discussion took place as to the origin of the deposit, and in the end it was generally conceded that we were dealing with the infilling of a swallow hole, but no one could even guess the age and the origin of the infilling material. No rocks are known in the neighbourhood which could yield such fragments. The journey was continued towards Cefn-y-Fedw and Trevor, and the Carboniferous series between the Mountain Limestone and the Coal Measures was examined. Tea was provided at the "Australian Arms," Trevor, and sufficient time was found to visit a fine section of Coal Measure Shales in brick works near the station. Saturday, August ISt.-Carriages left the" Wynnstay Arms" at 9. I 5 a.m, for Selattyn. Passing Brongyntyn Park the Glacial mounds of Old Oswestry and the surrounding fields were noticed, and the undulating character of the country showed the irregular manner in which the ice laid down its burden of gravels and sands on the flanks of the hills. After passing through the village of Selattyn the carriages were left and a detour was made across the deep ravine of the Morla's River to a quarry on the roadside north of the stream. Here the beds consisted of bedded cherts overlain by breccia and containing a sparse fauna of D, age. The rocks were EXCURSION TO THE BERWYNS. 51 strongly impregnated with secondary silica. So firmly were the pebbles in the breccia held by the siliceous matrix that fractures caused by earth stresses split across the included fragments. As the broken surfaces were covered by secondary silica it was con­ cluded that open joints had been produced which admitted of the percolation of siliceous waters. An attempt was made to determine the immediate cause of the jointing. A small fault, running at right angles to the lines of fracture, seemed to have puckered the beds into an anticline, and this must necessarily result in a state of tension being produced in the uppermost layers. In any case the order of events leading up to the jointing was clearly established. First the deposition of siliceous gravels in a calcareous matrix, then a replacement of the calcareous material by silica and the formation of chert, then local faulting and the production of open joints, and finally a continuation of siliceous deposition in the spaces left after jointing. On recrossing the valley, the limestone quarries of Craignant were visited. The palaeontological horizon of the beds is im­ mediately below the chert beds just described and has been assigned to Do. In the south quarry a fine colony of Lithostrotion irregulare is exposed on the working face.