LOCAL SURFACE AND UNDERGROUND SPRINGS. 169 



themselves varies much. For instance, at a spring at Rick- 

 ford, on the north slope of the Mendips, which has its 

 gathering ground doubtless in the direction of Burrington 

 and Blackdown, the spring issues direct out of the face 

 of the Mountain Limestone in close connection with the 

 Dolomitic, and is very quickly affected by the rainfall 

 upon its area, gushing out in large quantities = 8-10 million 

 gallons per diem after heavy rainfalls, and receding as 

 quickly and almost ceasing to flow in dry-weather periods. 

 Mountain Limestone, as is well known, abounds in vertical 

 jointings, which carry the water down quickly into the 

 underground basins and cavern-like formations met with in 

 that formation. Again, in chalk and sandstone districts, 

 especially in the Keuper and New Red Sandstone, the water 

 wells up in numerous small springs, and very often these 

 springs have to be collected together to bring them into a 

 focus for delivery and use. Such springs, which I have had 

 to deal with, occur in the north-east flanks of the Mendips 

 at Sherborne, where a spring is collected issuing from the 

 New Red Sandstone and Dolomitic conglomerate = IJ 

 million gallons per diem. Again at Backwell and Chelvey, 

 where they ooze out in swampy and marshy levels or flats in 

 accordance with the amount of drainage area they command, 

 they are equal to six or seven million gallons per diem ; and 

 in the Nailsea Basin, lying to the north of Backwell, we 

 have a good deal of water stored in the Pennant Grit 

 overlying the coal measures, which is a source of difficulty 

 in winning the coal in that basin. 



The flow of surface springs is very often affected by 

 barometrical pressure ; for instance, we often hear it said 

 in the country that when the wind is in a certain quarter 

 the springs are affected and flow less freely for a time, 

 and vice versd. When this comes to be inquired into, the 



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