142 PROCEEDINGS OF THE COTTESWOLD CLUB 



having occurred for over 2 years previously. No indica- 

 tion of such an excessive fall however was noticed at 

 Tewkesbury. 



A short distance below the junctions of the rivers the 

 Severn comes on to the Bunter beds of the Trias, and at 

 Shrewsbury passes over a patch of Permian. (These 

 rocks here overlie the coal measures.) It is afterwards in 

 contact with the lower Trias again, the Middle Silurian 

 Sandstone in the neighbourhood of the Wrekin and the 

 Wenlock Shale for a few miles, and at Ironbridge is on 

 the Coal Measures which crop out here. It is afterwards 

 on the New Red Rocks until it reaches the lias which 

 forms one bank of it near Tewkesbury whilst the Keuper 

 Marl forms the other. 



The Perry 10 miles long, the Tern 23 miles long, with 

 its branch the Roden 20 miles long, as well as the Worf 

 13 miles long, and the Stour 20 miles long, all flow chiefly 

 over the mottled sandstones and conglomerates of the 

 Bunter, with occasional touches of the Permian and 

 Keuper. 



The Salwarp comes entirely from Keuper Marl. On 

 the other side the Teme passes successively over Upper 

 Silurian Rocks, old Red Sandstone and New Red Marl 

 receiving tributaries from the same Rocks. The (Upper) 

 Avon differs from all the other tributaries previously 

 mentioned m draining large areas of Lias formation as 

 well as considerable areas of Keuper. The Lias Rocks 

 give the waters of the Avon a totally diff'erent quality to 

 any water that has been received by the Severn hitherto, 

 the water of the Avon being much less pure organically, 

 owing partly perhaps to the slowness of its flow. It has 

 also a far greater hardness than the Severn itself or either 

 of its other tributaries. 



The Pollution of the Severn 



Throughout its course the Severn receives numerous 

 pollutions from the towns and factories that stand on its 



