90 PROCEEDINGS OF THE COTTESWOLD CLUB 



physical or geological conditions, in no place mountainous, 

 and having a generally even slope or fall throughout. 



The flow of the river is not interrupted in any part of 

 its course by rapids or falls, beyond the numerous weirs 

 which greatly add to its purification, through the process 

 of more rapid oxidation through passing over the weirs. 

 The rainfall is fairly equal throughout the year, the mean 

 being about 28 inches. 



The porous rocks of the Cotteswolds carrying down the 

 percolated rainfall may be regarded as underground 

 conduits, the depth of which is the thickness of the 

 permeable rock, the width being that of the extent of the 

 strike, or its horizontal extent, and the inclination that of 

 the dip of the rock. 



Examples of such conditions of water-bearing horizons 

 or planes exist in the Upper Thames Basin, throughout 

 the area occupied by the Lias from west to east, up to 

 900 feet above the sea. The Inferior Oolite is at times 

 onlv fully saturated at its base, and the water following 

 the dip escapes — as at the large Syreford spring, 600 feet 

 above the sea. 



Still further eastward the water contained in the Great 

 Oolite is supported by the non-porous Fuller's Earth, and 

 does not rise to the top of that rock until it passes 

 beneath the Forest Marble, east of Northlcach. Eastward 

 still the Fuller's Earth thins away, and the two permeable 

 rocks or water-zones formed by the Inferior and Great 

 Oolite unite and pass under the thick impermeable Oxford 

 Clay, between the Windrush and the Thames ; these 

 again underlying the Corallian Oolites, which in their 

 turn pass under the Kimmeridge Clay east of Oxford. 



The intervention of faults, loss in continuity, or thinning 

 away through deposition, or undulations in the strata all 

 seriously affect the value of the springs governed by the 

 Fuller's Earth over the northern half of the eastern slopes 

 of the Cotteswolds. 



