PROCEEDINGS OF THE COTTESWOLD CLUB 59 



Thus after a run of nearly 15 miles less water was 

 delivered than at its source, and at 20 miles from its 

 source, where it joins the Thames at Cricklade, the river 

 only delivered no cubic feet per minute, or 1,000,000 

 gallons per dav. This incontestably shows the influence 

 of underground drainage and flow, due to the nature of the 

 underlying impervious clays of the Upper Lias, which 

 here on passing Colesbourn and Rendcomb, ceased to throw 

 out springs where their presence terminated : the w^aters of 

 the succeeding Great Oolite and Forest Marble from 

 this point were retained by the underlying Fuller's Earth, 

 and delivered at Trinity Mill and Baunton, north of 

 Cirencester. 



Thus south of Baunton much of the water of the Churn 

 is lost, becoming subterranean, being here held up by 

 the Fuller's Earth, thus separating two distinct under- 

 ground flows, until brought into communication with the 

 east and west Faults that intersect the valley above and 

 below Cirencester to Siddington and South Cerney, and 

 doubtless influencing the prolific springs at Boxwell. 



Ampney, Marston, and Marston Maisey Basin 

 AND Springs 



The drainage area of this prolific water district is about 

 40 square miles — these springs rise in the Forest Marble 

 four miles east of Cirencester, and after receiving many 

 small tributaries during a course of 10 miles, both the 

 Ampney and Marston Streams cross the Cornbrash, the 

 Ampney at Eastington and Poulton, the Maisey at 

 Maisey Hampton. They both then flow over the Oxford 

 Clay to the Thames east of Cricklade, the Ampney at 

 Eisey Chapel, the Maisey one mile west of Castle Eaton. 

 The chief supply of these streams is from five springs 

 issuing from the Great Oolite and Forest Marble at 

 Ampney Crucis, Ampney Park, Hunt's Hill, and Ampney 



