PROCEEDINGS OF THE COTTESWOLD CLUB 87 



As regards the Upper Basin above Lechlade, Mr 

 Taunton in 1867 ascertained by gaugings that the 

 inaximiun flow of the Thames at Lechlade is 28 times the 

 summer flow, which may be calculated at about 26,000,000 

 gallons per day. 



The floods of the upper parts of the Thames naturally 

 accumulate above Goring, where the narrow or contracted 

 passage through the Chalk Hills commences, and should 

 heavy rains in the Middle Basin, below Wallingford, 

 continue to fall while the accumulated waters from above, 

 or north and north-west of Oxford, are coming down 

 freely, it at once causes a large addition spreading over the 

 alluvial bottom at the foot of the Chalk Hills, and over 

 the alluvial land bordering the Thames to and far below 

 Reading. 



The extended and varied watershed of the Upper 

 Thames determines it to be a " river of floods," almost 

 from its source, increased by flood and land drainage 

 brought down by the Ray and Cole and other smaller 

 water courses above the navigation or to Lechlade. The 

 Lower Oolitic Rocks which rise from beneath the outcrop 

 of the Oxford Clay to the north of the Corallian beds, 

 which again crop out from beneath the Kimmeridge Clay, 

 in the Valley of the Ock, rise at so low or slight an angle 

 from beneath these Clay beds, that in wet seasons these 

 calcareous strata become so charged with water as to 

 throw it from their surface, either as floods or by land 

 drainage. These pervious beds then assume the drainage 

 character of non-retentive strata, and in addition to this 

 the Fuller's Earth and Clays of the Forest Marble in 

 the higher parts of the watershed produce the same eflect, 

 as also the flood-waters from the largely exposed surface of 

 the Lias Clays in the upper Valleys of the Windrush, 

 the Evenlode, and Cherwefl. The large tract of Oxford 

 Clay within the watershed of the Ray (Cherwell), and 

 from the Kimmeridge and Gault Clays in the Valleys of 



