THAMES, the most important river in Great Britain, rises in the central part of England, and flows eastward into the Germau Ocean. Our description will comprehend a notice of its basin, course, and effluents, and its commercial importance.
Basin.—Tho limits assignable to the basin of the Thames will depend on the place at which the mouth is fixed. We may consider as such the opening between Whitstable in Kent and the east extremity of Foulness Island in Essex, where the tideway has a breadth of 18 miles. Here the Thames opens into a large bay, separating Kent on the south from Essex and Suffolk on the north, and having for its extreme points the North Foreland in Kent and Orford Ness in Suffolk, 50 miles distant from each other. The basin of the Thames, commencing at Whitstable, is bounded by the high grounds which there run down to the coast, and form the cliffs east of that town. The boundary runs in a very irregular lino across the county of Kent and the Weald district of Kent and Sussex to the high ground on the tbern border of Ashdown Forest, in the latter county. From Asksdown Forest the boundary runs acress the high ground of Tilgate at Leonard's forests to Leith Hill in Surrey, and thence, In a very Irregular line, past the head of the "%Vey in Woolmer Forest to the yens. of the chalk downs near Alton, Hants. This boundary 'separates the basin of the Thames from the basins of the Sussex Ouse aad the Arun. From the nelehbourhood of Alton, the boundary of the basin la formed by the chalk downs which extend across Hants and Wilts by Basingstoke, Kingselere, Ilighclere,and Herbage, near Great Hedwin; and from thence by the downs which run north westward to the neighbourhood of East Kennet and Abury. From near Fast Kennet the boundary turns along the green-mod hills by Compton Basset and Chadderton ; and from thence to the western extremity of the basin near the commonly reputed head of the Thames amid the Cotswold Hills between Cirencester and Tetbury. From the neighbourhood of Tetbury the boundary rune northward along the ridge of the Cotswolds, to the head of the Churn (or true Thames), about three miles south from Cheltenham ; and from thence along by the same hills to near Campden, and by Long Compton 11111 and Edge H111 to the Arbury Hills near Daventry. at the northern extremity of the basin. From the Arbury Hills the boundary of the basin runs south to the neighbourhood of Bicester, and thence east went across Buckinghamshire, Bedfordshire, and Hertfordshire, along the Dunstable, Luton, and Royston downs, to the north-western comer of Emex. This ;Art of the basin of the Thames is drained by its affluents the Cherwell, the Theme, and the Lea. Au irregular line drawn through the county of Essex from its north-western corner, first eonth-sonth-east by Dunmow and Brentwood, and then east by Rayleigh and Rochford to the coast, will complete the boundary.
The greatest extent of this basin from oast to west Is from the mouth of the Thames to the neighbourhood of Tetbury, about 136 miles; the greatest extent from north to south is from the neighbourhood of Daventry, Northamptonshire, to that of Alton, Hampshire, about 78 mile.. The basin comprehends the whole or part of the counties of Kent, Surrey, Sussex, Hants, Berks, Wilts, Oxon, Bucks, Ilerta, 111,1dIenex, and Eeeex, with small portions of Warwickshire, North amptonshire, and Bedfordshire ; its area may be estimated nt about 000 square miles. The basin of the Thames is occupied wholly by the secondary and tertiary formations. The sources of the river and the course of its upper waters are in the oolitic beds of the Cotswold Hills. Owing to the entire absence of coal, the basin of the Thames has no manufactures except those of the metropolis; but it contains some of the richest agricultural districts in the kingdom.
Course and Affluents.--' Thames Head,' the spring which has com monly been regarded as the bead of the Thames, is about 3 miles S.W. from Cirencester, near a bridge over the Thames and Severn Canal, which is called Thameeliead Bridge ; ' hut that which is to be regarded as the true head of the Thames is about 3 miles S. from Cheltenham. Two streams rise, the principal one from several openings at a spot popularly called The Seven Springs, and the other from four springs near Ullen Farm, the westernmost of which springs is the remotest head of the river : both streams rise on the south eastern elope of the Cotswolds, and form by their junction, about a mile from their respective sourcee, the river Churn. At Cricklade, 20 mile. S.E. from its source, the Churn joins the commonly reputed his or Thames, the length of which above the junction is only about 10 milec From Cricklade the river flows 9 or 10 miles east-north east to Isechladt. Jnnt above Lechlade it receives, on the left bank, the Color, from the Cotswold Hills, east of Cheltenham; and below Lechlade it receives the Lech, or Leach, which also rises in the Cotswolds. From Lechlade the Thames flows 14 miles eastward to the junction of the Windrush. The Windrush rises in the Cotswolds between \Vinchcombe and Carnpden, and after a course of 34 miles joins the Thames on the left bank. Below the junction of the Wind rush the Thames receives on the left bank the Evenlode, which rises In the Cotswolds near Moreton-in•the-Mareli, and receives the Olyme, which flows through Woodstock and Blenheim Park. The Thames then turns south, and flows to Oxford, where it joins the Cherwell. The Cherwell rime in the Arhnry Hills, near Davenport in North amptonshire, and flows southward by Banhury : it joins the Thames on the left bank.