PROCEEDINGS OF THE COTTESWOLD CLUB 89 



point, the tributaries are so numerous and their watersheds 

 so various that any estimate of their volume, at different 

 seasons would be difficult, and in flood almost defy 

 calculation. 



The geological condition of the sources of the Churn 

 which rises just within the western escarpment, is the 

 type of most of the streams which derive their head waters 

 from these Jurassic strata. It is from the aggregation of 

 such streams and springs that the Churn, the Coin, 

 the Windrush, the Evenlode, and Cherwell, etc., derive 

 their supply, and in this way become perennial. The 

 Churn and the Coin with their affluents specially come 

 within this general description, and in detail more so 

 than any of the Cotteswold streams. 



The Swindon Ray and Cole receive their waters from a 

 different source, and are types of streams flowing from 

 south to north. They rise at the foot of the escarpment 

 of the Chalk Range, flanking the Vale of the White Horse 

 to the south and flowing over the Upper Greensand 

 Gault and Lower Greensand, thence running over a very 

 large surface of Kimmeridge Clay, cutting their courses 

 through the Corallian Oolites of Shrivenham and High- 

 worth, then passing over the wide expanse occupied by 

 the Oxford Clay. The Ray reaches the Thames near 

 Water Eaton, east of Cricklade ; and the Cole opposite 

 St John's Bridge and Weir, east of Lechlade. The 

 volume of perennial waters received from the cretaceous 

 rocks by these rivers is shown by several mills near their 

 sources and they largely contribute to the amount of flood- 

 water from the Kimmeridge and Oxford Clays in the 

 Swindon Basin. 



Hydrological Conditions, &c. 



The Thames well illustrates the condition of river 

 flow, its water supply being derived from numerous 

 sources or feeders, and this from an area of known 



