242 



I have separated the district called Bampton from that of the 

 Windrush and of the Evenlode, because the brooks and rivulets 

 in it, do not finally form a river of much larger size, and then 

 pass on, and into the Thames; but several small brooks take 

 their course into the Thames without uniting, and this renders 

 it incapable of being designated the watershed of any particular 

 brook or river. 



The same will refer to the district called Highworth. 



The area of the Watershed of the Upper Thames, thus 

 described, is 875 square miles, and is made up as follows : — 



WEST OF THE THAMES. 

 Swillbrook and Thames Head 



NOETH OF THE THAMES. 



The Chum 



Ampney and Marston Brooks 



TheCoki 



The Leach 



The Bampton and Thames Valley District 



The "Windrush 



The Evenlode 



SOUTH OF THE THAMES. 



The Ray 



Highworth District ... 



The Cole 



Square Miles. 

 ... 74 



73 



32i 



87 



36A 

 119 

 141 

 189 



65A 



48 



875 



The rainfall over this 875 square miles may be taken at 28 

 inches per annum, from which 12 inches should be deducted for 

 evaporation. The rainfall on a square mile, with this deduction, 

 will be 1,376,710 cubic yards. But to arrive at the probable 

 available quantity, a further deduction should be made for 

 percolation into porous strata, which may not afterwards be 

 thrown out by springs, and, in consequence, may not reach the 

 Thames, but pass under it. Some of this water we know must 

 be brought to the surface by faults, as at Boxwell Spring, but 

 this can only be part of what percolates through the beds of the 

 Upper Oolite to the surface of the Fullers Earth. The water 



