4 PHYSIOGRAPHY. [chap. 



At Lechlade the quantity of water running down the river 

 has been roughly estimated at something like a hundred 

 million gallons per day, or only about one-fourth the 

 quantity flowing over Teddington Weir. The main stream 

 splits up at Lechlade into a number of smaller streams, 

 forming the "head-waters" of the river, and it is by no 

 means easy to say which of these streams should be 

 followed up in seeking the true source of the Thames. 

 Nor does it much matter, for the origin of any one of 

 tJiem is much the same as the origin of any of the others. 

 It is usual, however, to single out one of these streams, 

 which takes its rise in a spring near Cirencester, about 170 

 miles from London Bridge, and is dignified with the name 

 of Thames Head. 



Although the spring at Thames Head is thus popularly 

 called the " source " of the river, it should be remem- 

 bered that the quantity of water delivered by this 

 spring is quite insignificant when compared with that 

 derived from the numerous streams which flow into the 

 Thames at various points along its course. Every 

 tributar)' helps to swell the bulk of the river by dis- 

 charging its water into the main stream ; yet it does not 

 follow that the river is necessarily increased in width by 

 the influx of this water, for it often happens that the 

 additional supply is carried off by increased rapidity of 

 flow. As the Thames rolls along, it receives a number 

 of these feeders, or affluents^ which empty themselves 

 into the river, some on one side and some on the other. 



^ Affluent,{xoxa.\^t\.^X\x\.ad ^rvAfliw, "to flow." The junction of an 

 affluent with the main stream is termed the confluence, or place where 

 they "flow together." Thus, the town of Coblentz takes its name from 

 the Latin form Confluentes, in allusion to its position at the junction of 

 the Moselle and the Rhine. 



