ENGLAND 



2910 



ENGLAND 



and Crouch are thus the relics of 

 longer streams which drained 

 from the chalk ridge eastwards to 

 this parent stream. The Kennet 

 rises in the angle where the Chil- 

 tern and Downs chalk ridges 

 meet in the Maryborough downs, 

 and flows in a straight course to 

 the Thames at Reading in the 

 general line towards Southend. 

 This is the real lower Thames, with 

 all the left bank tributaries, Colne, 

 Lea, etc., coming down from the 

 chalk across the London clay. 



The upper Thames makes a 

 great break through the chalk 

 at the Goring Gap to reach Read- 

 ing, and the shape of its basin in 

 the Oxford clay plain between the 

 Cotswold oolitic ridge and the 

 Chilterns is due to the general 

 drainage to the S.E. and the side- 

 ways drainage in the clay hollow. 

 River System and Market Towns 



The Churn, Coin, Leach, Wind- 

 rush, Evenlode and Cherwell and 

 the Thames itself between Oxford 

 and Reading flow to the S.E. ; the 

 Ray and the Thame (vale of 

 Aylesbury), the Ock (White Horse 

 vale), and the Thames above 

 Oxford flow at right angles to this 

 main direction across the clay. 



The Wealden rivers rise along a 

 water-parting which roughly fol- 

 lows the line from Hythe to Hind- 

 head. From the northern clay vale 

 the Wey, Mole, Medway and Stour 

 cut through the N. downs. The 

 Arun, Adur, Ouse and Cuckmere 

 stft through the S. downs to the 

 ! English Channel. The Rother 

 alone is entirely on the Weald, and 

 crosses the Hastings sand. 



The Itchen, Test, Avon, Stour 

 and Frome flow from the chalk to 

 the Hampshire basin. The Avon 

 drains Salisbury Plain. All around 

 the coast from the Wash to Poole 

 harbour the rivers reach the sea 

 along a low coast, where the rise 

 and fall of the tides makes a great 

 difference to each estuary. 



The river system in general has 

 determined the situation of the 

 market towns. Guildf ord, Arundel, 

 and Lewes are gap towns on the 

 downs. Oxford, Reading Chelms- 

 ford and Norwich have each been 

 influenced by the confluence of 

 two streams. 



The peninsular rivers of the S. W. 

 are developed from the Exmoor, 

 Dartmoor, and Bodinin moor- 

 lands. The Tamar and Torridge, 

 rising in the Ditchen Hills inland 

 from Hartland Point, are excep- 

 tions ; the valley of the Tamar 

 makes a lowland way across the 

 peninsula. Falmouth Bay is a 

 typical Cornish estuary. The 

 rivers of the oldest rocks in Eng- 

 land are tiny streams which flow 

 into large rock-walled estuaries 



which are the drowned valleys of 

 the middle or lower courses of 

 the streams ; they indicate a period 

 when the streams were larger, 

 longer, and more powerful, and 

 which preceded the inflow of the 

 sea or the sinking of the coast. 

 The Camel estuary is the only 

 large break in the iron-bound coast 

 of N. Cornwall between St. Ives 

 and Hartland Point ; here miles 

 of sand at low water attest the fact 

 that the estuary is too large for 

 the tiny stream which drains into 

 it ; the river and estuary are not 

 conformable. 



The Parret, Brue, Axe, and 

 Bristol Avon belong to an area 

 where many geological formations 

 are crowded together. The Parret 

 is bounded S. by greensand hills, 

 like Leith Hill in the Weald ; the 

 Brue and the Axe belong to Sedge- 

 moor, a fen district in miniature 

 with the limestone Mendip Hills 

 to the N. The scenery of the 

 Mendips repeats that of the Peak 

 district, with lead mines, swallow 

 holes, and caverns. The Cheddar 

 Gorge is, however, without parallel 

 in Derbyshire ; the cliffs are prob- 

 ably the sides of a great cave of 

 which the roof has fallen. The 

 Bristol Avon rises in the oolitic 

 Cotswolds, crosses the S. portion 

 of the Oxford clay plain, cuts a 

 gorge through the oolite, crosses 

 a lias clay plain, and cuts a second 

 gorge at Clifton through the car- 

 boniferous limestone of the Bristol 

 coalfields to the Bristol Channel. 

 The Severn and Thames 



The Severn is a Welsh river of 

 which the middle and lower courses 

 are English. It originated prob- 

 ably as one of a series of streams 

 which flowed in a general S.E. 

 direction from the Cambrian mts. 

 The young stream, in all prob- 

 ability the parent stream of the 

 Thames, flowed across a slope 

 where the surface features were 

 of small magnitude. In time the 

 softer clay rocks of the lias and 

 the oolite were worn away, leav- 

 ing outstanding sandstone and 

 limestone hills and ridges. Strug- 

 gles were initiated between the 

 streams and the harder rocks ; 

 there was a chance that the Cots- 

 wold and Chiltern ridges would 

 cut the young stream into three 

 sections. The Goring Gap was 

 cut through the chalk, but no gorge 

 was made in the oolite, and the 

 young stream grew into two rivers 

 the Thames and the Severn. On 

 the one hand the Severn is parallel 

 to the Cotswolds and the general 

 lines of the T"bame, Thames, and 

 Upper Bristol Avon ; on the other, 

 it lies on the lias clay, close to the 

 edge of the Trias, and is related in 

 this respect to the lower Trent. 



The vales of Evesham and Berke- 

 ley resemble the vales of Newark 

 and York. Above the confluence 

 with the Stratford Avon between 

 Tewkesbury and the Coalbrook- 

 dale Gorge at Ironbridge, the 

 Severn valley belongs to the 

 Trias ; the Worcester plain is 

 like the plain of Burton on the 

 middle Trent, The Teme, Wye,, 

 and Usk may be considered as 

 Severn tributaries. In their Eng- 

 lish sections they cut valleys in the 

 Old Red Sandstone. 



Lancashire and Cheshire Estuaries 

 The Triassic plain of S.E. Lan- 

 cashire and Cheshire is drained by 

 the Mersey and its affluent the 

 Irwell, the Weaver, and the lower 

 Dee. Their outlets to Lancashire 

 Bay, the Mersey and Dee estuaries, 

 are not conformable with the 

 streams themselves. In both cases 

 the estuaries are being silted up, 

 sandbanks a few feet below the sea 

 continue the Wirral peninsula far 

 to the N., the main channel wind- 

 ing at low water as a narrow stream 

 across the sand-choked Dee estu- 

 ary. The bottle-neck formation of 

 the Mersey estuary assists the daily 

 scour of the tides, but large dred- 

 gers have to be maintained to 

 provide a regular channel for 

 liners. Ribblesdale belongs to the 

 mountain limestone of the Pen- 

 nines, and connects with Airedale 

 at the Aire Gap. 



Lonsdale is a reminder that the 

 Lune is a Pennine stream with a 

 silt-filled estuary. The tiny streams 

 of the Lake District which reach 

 Morecambe Bay are really longer 

 than the map indicates, since they 

 form definite valleys across More- 

 cambe sands and have lower 

 courses which are only obscured at 

 high tide. The Eden rises close to 

 the sources of the Swale and Ure, 

 flows across Permian sandstone to 

 the Triassic Solway Plain ; its afflu- 

 ent, the Irthing, completes the 

 Tyne Gap in the Pennines. Like, all 

 the Triassic bays, Solway Firth has 

 vast stretches of sand exposed at 

 low tide. The Lake District cul- 

 minates in Scawfell, but the lake 

 valleys radiate from Helvellyn. 

 Windermere, Coniston Water, 

 Wastwater, Bnnerdale Water, 

 Buttermere, Derwent Water, Bas- 

 senthwaite, Thirlmere, Ullswater, 

 and Hawes Water are typical lakes 

 of a glaciated area, and fill part of 

 the narrow dales which lead down- 

 wards between tree-clad ridges 

 from the central dome where an- 

 cient sedimentary rocks are exposed 

 in Skiddaw, and intrusive volcanic 

 rocks raise weathered peaks, as at 

 Scawfell. Walney Island and the 

 coast from Foulney Island to 

 S. Bees Head is Triassic low- 

 land. Windermere, Ambleside and 



