NOTES ON FEATURES OBSERVABLE ON THE MAIN LINES OF RAILWAY.

Our different lines of Railway have largely aided the progress of Geology, partly because they have opened up a ready means of communication to all parts of the country, but mainly because they have furnished some of the most important and instructive geological sections; yet while it would be impossible to attempt an enumeration of them, it may be interesting to point out some of the leading features observable on the great lines of railway.

Thus, in travelling from London along the main lines. with the aid of a geological map, the character of the scenery may be studied with advantage in connection with the geological structure.

Great Eastern Railway.-Travelling by way of Colchester on the Great Eastern line we pass by the Thames Valley deposits-brickearth and gravel-near Stratford and Ilford, famous for their mammalian remains, and beyond Romford we get upon the bare London Clay, capped at Brentwood, in the deep cutting, by the Lower Bagshot beds. From this station to Ipswich we pass over the London Clay, covered here

Mendip Forest; on the Poikilitic strata, Delamere Forest (around Northwich and Chester), the Forest of Arden (Warwickshire), Needwood Forest (Staffordshire), Sherwood Forest (Nottinghamshire), North Petherton Forest (around Bridgewater); on the Liassic strata, Neroche Forest (including that of Ashill, to the west of Ilminster); on the Oolitic strata, Braydon Forest (west of Cricklade), Wychwood Forest (around Chipping Norton, Burford, and Whittlebury), Selwood Forest (between Frome and Wincanton), and Gillingham Forest (Dorset); on the Wealden strata, St. Leonard's and Tilgate Forests (near Horsham and East Grinstead); on the Gault and Greensand, Woolmer Forest (east of Selborne), Holt Forest (east of Alton); on the Tertiaries, the New Forest (Hampshire), Savernake Forest (Wilts), Windsor Forest (Berkshire), and Epping and Hainault Forests (Essex).

and there by Drift Gravel and Boulder Clay. Thence we cross

over the Chalk, similarly capped by Drift, until we reach Norwich.

Proceeding from London by Cambridge we travel for some distance along the valley of the Lea, filled with Alluvial deposits, and bounded by low Tertiary hills capped with Drift, and we reach the Chalk near Bishop's Stortford. Thence in journeying to Norwich we pass over the Chalk, the lowest beds of which are seen at Cambridge, and between Ely and Brandon over the Alluvium; beyond which we cross the Chalk with Drift-beds which almost entirely cover the higher grounds, while in the valleys occur old Alluvial deposits which have yielded, as near Thetford, some of the earliest types of flint-implements formed by man.

Great Northern Railway.--On the Great Northern line we pass through tunnels and cuttings of London Clay as far as Hatfield, the bordering hills being capped by Drift Gravel and Boulder Clay as at Finchley and Barnet. Beyond Hatfield we pass over the Chalk with much gravel, chiefly that called Middle Glacial, and between Hitchin and Potton we cross the Lower Cretaceous beds; thence through Huntingdon and Peterborough to Stamford, we traverse a low-lying tract of country formed of Oxford Clay and Alluvium. Beyond this, and as far as Grantham, we cross the Lower Oolites, which near that town are well displayed in the cuttings in the Lincolnshire limestone, as are also the Boulder drifts (see p. 307). Passing over the Lias we reach Newark, situated near the junction of Lias, Rhætic Beds, and Red Marl. The Marls here yield much gypsum, which is worked for plaster of Paris. Thence we continue in the vales formed of Triassic and Permian strata, with some alluvium, by York, Northallerton, and Darlington. Through Durham, Newcastle, and Morpeth, we traverse the Coal-measures, and beyond these towns the line passes over the Lower Carboniferous

series with the coal-bearing representatives of the Mountain Limestone near Berwick-on-Tweed.

Midland Railway.-Starting from St. Pancras, we travel over the London Clay through Hendon, and Boreham Wood, until we cross the outcrop of the Reading Beds and reach the Chalk at Radlett station. Here a large pit by the railway shows the London Clay and Reading Beds capped by Drift Gravel (Middle Glacial); and in the park adjoining the Hertfordshire puddingstone was, at one time, very well shown in a pit. Proceeding towards St. Albans, we cross the Chalk, almost entirely obscured by deposits of Gravel and Brickearth (Middle Glacial), and thus we continue until beyond Luton, we traverse the Gault, and near Ampthill the Lower Greensand. Further on we come upon the Oxford Clay, and soon reach Bedford, which is situated on the borders of this Clay and the Lower Oolites. The gravels in the valley of the Ouse have yielded remains of Hippopotamus, etc., and some flint-implements, through the labours of Mr. J. Wyatt. Near Wellingborough we enter a valley which exposes the Lias, while above it come the Northampton Sands, now so largely worked for iron-ore. From Market Harborough to Leicester we cross the Lias, much obscured by Drift, but the lower beds, worked for cement-stones, are well exposed at Barrow-on-Soar, where the junction with the Rhætic beds may also be seen. At Mount Sorrel station we pass in view of the slaty and granitic hills of Charnwood Forest (to the west), and proceed across the Red Marl by Trent to Derby. Thence skirting the south-western corner of the Derbyshire Coal-field, we enter the Dale country at Matlock, passing for the most part through grand scenery in the Carboniferous Limestone from Bakewell by Monsal and Miller's Dale to Buxton. Then we proceed through the southern extremity of the Lancashire Coal-field (sometimes called the Cheshire Coal-field) by Stockport to Manchester.

London and North-Western Railway.-By the London and North-Western line we pass through the London Clay at the Primrose-hill tunnel, and thence across a thinly populated tract of country formed of the same deposit until we reach Watford, where the Reading Beds and Chalk are seen.

Several fine exposures of Chalk are then passed through in the cuttings, and near Ivinghoe the Upper Greensand and Gault are reached. At Leighton Buzzard we proceed over the Lower Greensand, and thence through the Oolitic country of Fenny and Stony Stratford, coming on to the Lias here and there in the deeper valleys, and crossing its broad outcrop near Daventry and Rugby.

Rugby is situated near the outcrop of the Rhætic or Penarth Beds, beyond which we traverse the marls and sandstones of the Trias, covered in places with much Drift gravel. Between Nuneaton and Tamworth we skirt and finally cross over a portion of the Warwickshire Coal-field, beyond which, by Lichfield, Stafford, and Crewe, we chiefly pass over Triassic beds with Drift gravels. Near Crewe the Upper Triassic beds yield the rock salt and brine springs. Beyond Crewe we continue over the Triassic beds by Warrington, cross the South Lancashire Coal-field near Wigan, and traverse the Triassic beds again through Preston on the borders of Alluvial flats.

At Lancaster the Coal-measure rocks are again reached, and further north we enter upon the Carboniferous Limestone as far as Kirkby Kendal. Beyond this we pass through the Silurian and Cambrian district, with traces of Old Red Sandstone, and more Carboniferous Limestone between Shap and Penrith. Here we enter upon the Permian rocks of the Vale of Eden, which, near Carlisle, are capped by Red Marls, Rhætic beds, and Lias. (See p. 122.)

If after reaching Rugby we proceed by Coventry to Birmingham, we cross different members of the Trias and Permian, and then traverse the 'Black Country' of the South

Staffordshire Coal-field to Wolverhampton. Thence we skirt the borders of the Silurian rocks of Wenlock and the Cambrian of the Longmynd at Wellington and Shrewsbury, and continue partly on the Triassic and Permian rocks and partly on the Coal-measures by Wrexham to Chester, and thence by the sea-shore round the Palæozoic rocks of North Wales to Bangor, and so on to Holyhead.

Great Western Railway. Along the Great Western Railway for some distance, as far as and beyond Slough, we traverse the gravels and brickearth of the Thames Valley. At Maidenhead we reach the Chalk, and continue upon it as far as Reading and Moulsford, with the escarpment of lower Tertiary beds to the south. Beyond Moulsford we cross the Upper Greensand on to the Gault; Didcot being situated near the junction of the two. Thence, as far as Chippenham, the line passes for the greater part over low-lying clayey tracts of Gault, Kimeridge, and Oxford Clays. Thence we enter upon the Lower Oolitic country forming the southern extremity of the Cotteswold Hills, which rocks form such fine bold scenery in the valleys west of Chippenham and around Bath. The large quarries of Corsham and Box, and the long tunnel between the two, are situated in the Great Oolite.

At Saltford the Lower Lias and White Lias (the upper portion of the Penarth or Rhætic beds) are exposed; near Keynsham there are cuttings of Lias; and between this and Bristol most of the cuttings and tunnels are excavated in the Pennant Grit or Middle Coal-measures of the Bristol coalfield.

Leaving Bristol we traverse the little coal-field of Nailsea, and then proceed along the Alluvial flats that border the estuary of the Severn with little relief as far as Bridgewater. The cutting at Uphill, however, where the western extremity of the Mendip Hills is traversed, shows a fine cutting of

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