PROCEEDINGS OF THE COTTESWOLD CLUB 55 



minimum flow of 20,000,000 gallons per day passing over 

 St John's Weir from the area drained by the 5 basins 

 above Lechlade, or 



The basin of the Upper Thames 

 „ ,, Coin 



„ „ Ampney and Marston 



„ ,, Cole and 



,, „ Swindon Basin 



or prior to the large accession of water derived from the 

 Leach, the Bampton Streams, the Windrush and Evenlode, 

 which join the Thames below Lechlade, and before 

 reaching Oxford ; and finally uniting with the Cherwell 

 immediately below the City. 



Bensington Weir above Wallingford receives and passes 

 over the entire volume of water of the Upper Thames and 

 its tributaries. This extensive weir separates the derived 

 waters of the Jurassic rocks from those of the Cretaceous 

 or the Middle Thames Basin. 



From the Jurassic Rocks alone above Lechlade we have 

 reason to believe that the ordinary flow may be at least 

 from 30 to 50,000,000 gallons per day, and this must be 

 greatly exceeded during the winter and early spring 

 months. 



The loss by percolation through the Cornbrash, Forest 

 Marble, and Great Oolite is largely compensated by the 

 great discharge of water from the Fuller's Earth, which is 

 thrown out by the Baunton, Boxwell, Siddington, and 

 other springs on the Churn, the Forest Marble and Great 

 Oohte of the Ampneys, the many and fine springs from 

 nearly the entire length of the Coin, notably those of 

 Syreford, Bibury, and Coin St Andrews to the Thames at 

 Lechlade. 



As above stated the chief loss in the upper part of the 

 watershed is through the Great and Inferior Oolite, and 

 that from an area of nearly 350 square miles. 



