The corporation of the city of London has the almost uncontrolled conservancy of the Thames, and the regulation of its navigation and fishing. The navigation of the upper part of the Thames is kept up by locks and webs, tho lowest of which is at Teddington, which is consequently the limit of the tide. Teddington is about 13 miles above London Bridge. Vessels of 800 tons get up to the St. Kathe rine's Docks, and them of 1400 tons to Blackwell, about 6 miles below bridge. No river in the world equals the Thames in its commercial importance. The river for some two miles or more below bridge is crowded with vessels, chiefly coasters, steam-vessels of all sizes, and colliers, which moor alongside the guns's or in tiers in the stream ; and for larger vessels there are several docks excavated on the banks of the river. There is a dockyard for the navy (now little wed) at Deptford, about 4 miles below London Bridge; one at Woolwich, 9 miles below; one at Sheerness, in the Isle of Sheppey, at the junction of the Thames and Medway ; and one at Chatham, the most important of the four, on the Medway. Tho fortifications nt Sheer
ness, defend the entrance to both rivers. The passage of the Thames is further protected by Tilbury Fort, and that of the Medway by Gillingham Fort.
The width of the river at London Bridge is 290 yards. For nearly the whole way below London Bridge the river is embanked, and is almost throughout its lower course skirted with narrow marsh-lands. The width of the river at Woolwich, at high water, is 490 yards; at Gravesend Pier, 26 miles below London Bridge, it is 800 yards; at Coal-house Point, three miles below Gravesend, it is 1290 yards; it then gradually increases to the width of about 6 miles at the Nore, and to 18 miles at the point where we have fixed the mouth.
It is a common opinion that this river in the upper part of its course is properly called Isis, and that it is only below the junction of the Theme that it is called Thames, which name is said to be formed by combining the two names Theme and Isis. But this is a mistake; the name Isis never occurs in ancient records.