or yards, but one of these at Thingvalla, more in the centre of the island, the Allmanagiá, has a throw of about 100 feet. In this case, the author is satisfied that the gid is due to the unequal settling of a crust of lava formed on the surface of a still fluid mass, which had found an outlet and flowed out after the solidification of the surface. He is not prepared however to say that this explanation will hold good in the case of all the rifts on the Reykjanæs peninsula. It certainly would not in the case of the great fissure from which the Skapta lava was erupted. Consequently any clear case of the formation of a new gid in strata long cooled and solidified would have been well worth investigation.

From a careful examination of the locality it appeared that no fresh formation of a giá has taken place, but that certain small portions of the rock on which the lighthouse stands had been loosened partly by ordinary denudation and partly by earthquakes, which are frequent here, and had fallen on to the beach. The strata of partly consolidated volcanic ashes and lava are quite continuous at the end of the small cove or recess between the two large rocks above referred

to.

ON SOME SECTIONS IN THE LIASSIC AND OOLITIC ROCKS OF YORKSHIRE. BY JAMES W. DAVIS, F.G.S., F.S.A., ETC., HONORARY MEMBER

OF THE NEW ZEALAND INSTITUTE.

The upheaval of the Penine Anticlinal separating Lancashire and Yorkshire in a direction north and south; and the dislocation of the strata caused by the Great Craven Faults running east and west, have not only influenced the physical features of the West Riding of Yorkshire, but have also been instrumental in moulding the character of the country towards the eastern boundary of the County. The Carboniferous series were forced into a semi-circular basin, with a general depression towards the south-east, the Coal Measures were crushed and fractured in every direction, and innumerable faults exist as the result of this action. A long period of depression followed, and the several beds of the Millstone Grits and Coal Measures were denuded to a more or less regular surface, over which the Magnesian Limestones and other members of the Permian Series were unconformably deposited. They dip towards the east and disappear under the Keuper and Bunter Sandstones and Marls. The latter are in turn hidden beneath the thick glacial beds and river deposits which form the surface of the extensive plain of the river Ouse.

On the eastern side of the plain of the Ouse, the physical conformation of the country assumes a lofty character; the Liassic series of the North Riding, surmounted by the sandstones of the Inferior Oolites, give rise to an extensive area of undulating moorlands. reaching from Saltburn, in the north, to Emsley, Pickering, and Goathland Moors, in the south; towards Cloughton and Scarborough the sandstones are obscured by thick deposits of Boulder Clay and Gravel. Separating this upland area from the Vale of Pickering is a long range of tabular hills of the Coralline Oolites, extending from Hambleton to Scarborough; they form a bold escarpment to the northwards, under the base of which dip the sandstones of the Inferior Oolites. South of the Pickering Valley, filled with Post Glacial Gravels and Alluvium, extends the long line of escarpment of

Chalk Wolds. The Chalk has a general dip to the south-east of two to five degrees, but in several places this is interferred with by lines of faults, and contortions. The Chalk escarpment, after extending eastwards from Flamborough Head to North Grimston and Achlam Brow, takes a southerly direction to the Humber, enclosing the luxuriant plains of Holderness, a basin-shaped hollow filled with glacial and more modern deposits. It is thus seen that, as has been found to be the case in the primary rocks of the western uplands of Yorkshire, the Wolds and hills of the easterly portion of the County exhibit the highest or most recent strata occupying the inner margins of the basin; these are surrounded by the older series which successively rise from underneath, and occupy constantly enlarging circles, the lowest, the Lias, underlying and surrounding the whole. Whilst this general conformity can be traced throughout the series of strata, there are several foldings and dislocations which interfere with it, notably in the lower beds of the Lias and in the Chalk. The principal lines of disturbance in the Chalk have generally an east and west direction. One of the finest exhibitions of distorted strata occurs at Scale Nab, in the Bempton Cliffs, half way between Flamborough Head and Speeton. The cliffs are 250 feet in height, and the Chalk is folded repeatedly. Photographs of this magnificent section were issued to the members of the Society in the year 1885, and a brief description was printed in the Proceedings of the same year. The line of disturbance is indicated on the map of the Geological Survey as proceeding due west a little north of Wold Newton and Foxholes, and about midway between Sherborn and Weaverthorpe. In the railway cutting near Hunmanby the Chalk is brought by a fault into juxtaposition with the Neocomian beds of Speeton.

The general dip of the beds is towards the south, but there are variations. Southwards from Robin Hood's Bay the rocks have the normal dip, but about the middle of the Bay they are observed to form an anticlinal and roll over with a strong northerly dip. The anticlinal extends inwards from the coast through the middle of Eskdale; evidence of it may be seen in the Lower Lias Shale on the south bank of the river in the Blue Scar. The anticlinal crosses the

GREY

Cloughton
Wyke

Cristhorpe Cliff

LOWER

CALCAREOUS

CRIT OXFORD

CLAY

WELLOWAY

Red Cliff

CALE.G

OXFORD CLAY

BOULDER

OF. CLAY

White Nai

CLAY

river diagonally, and this causes a peculiar effect, the beds dip east in the eastern half of the dale and west in the western half. At the southern extremity of Robin Hood's Bay is the Peak Fault, by which the base of the Middle Lias is brought into a line with the top of the Upper Lias, indicating a throw of more than 400 feet. The indication of the fault inland is shown under Crag Hall, where the Dogger abuts against Grey Limestone. The country south is buried in Boulder Clays and the fault is difficult to trace. There are indications of it between Pye Rigg and Bell Hill, and southwards it runs west of Cloughton, where the Moor Grit, which crops out in the village, is also seen 100 feet higher, capping Ripley's Bank. The country south of Cloughton is covered with Boulder Clay, but it is probable that the faults occurring at Scarborough Castle may be a continuation of the same line of disturbance. At Hayburn Wyke there is an anticlinal which may indicate a branch of the Peak Fault, but its connection is by no means very clear. South of Scarborough the coast section exposes great thicknesses of Boulder Clay with the Estuarine Series and the Oxford Clay beneath, at White Nab and Osgodby Nab. At Red Cliff the fine section exposing the series from the Cornbrash up to the Lower Calcareous Grit is cut off by a fault which brings the Estuarine Series again into view at the northern extremity of Gristhorpe Bay. The Gristhorpe Cliffs, further south, afford a magnificent section of the strata between the Cornbrash and Kelloway Rock and the Lower Calcareous Grit. The section is continuous to Filey Brig, where the Passage Beds and probably the equivalent of the lower beds of the Coralline Oolites are exposed. South of Filey the Boulder Clays fill up the coast of the Bay, envelloping the Kimmeridge Clay (see fig. 1).

The drainage of the northern portion of the district is conveyed by the River Esk to the sea at Whitby. South of the valley of the Esk the River Derwent and its tributaries run into the Ouse; and the whole of this district is drained westwards, away from the coast, and eventually reaches the sea by way of the Humber. The Esk and its tributaries form a series of dales, of which the most important, Glaizedale, Fryup, Danbydale, and Westerdale are cut through the Oolitic Sandstones deep into the Liassic Rocks; about one hundred