MK. H. B. WOODWARD ON A WELL-SINKING AT SWINDON. 305 



parts per 100,000 of sodium chloride were thrown out " by a spring 

 in the Lower Lias," probably rising from the Coal-measures ; and 

 '' at Braysdown Colliery [near Radstock], 500 yards in depth, a 

 constant volume of water is met with, which Mr. Biggs found to 

 contain 1008 grains of common salt per gallon (or 1440 grains per 

 100,000) : the water appears to be derived from the Coal-measures, 

 and it is very salt indeed " *. Other instances might be given to show 

 that the presence of sodium chloride in the waters of wells at a 

 distance inland is not dependent on the proximity of the saliferous 

 jS"ew Red Rocks ; but it will be sufficient to mention the waters at 

 Moira, in the Leicestershire coal-field, the thermal saline water in 

 the " killas " at Camborn, in Cornwall t, and a spring on the south- 

 west side of Derwentwater, which issues from a bed of grit 

 (" Arenig Grit ") in the Skiddaw Slates J. 



Of course some of the saline waters may derive their ingredients 

 from saliferous Xew Red Rocks at a considerable distance ; for, as 

 Prof. Prestwich remarks, " Thermal springs in non-volcanic districts, 

 such, for instance, as at Bath and Buxton, may generally be considered 

 as natural artesian wells, where water, after descending through 

 permeable strata to great depths, escapes through fissures in the 

 overlying strata (the sides of faults or dislocations) to the surface. 

 The temperature of such springs, above the mean of the surface, is 

 necessarily proportionate to the depth reached by the descending 

 water ; and, as the Bath waters have a temperature of 120° Fahr., 

 we may assume the depth from which they rise to be about 3500 

 feet'"'§. In this case the shales at the base of the Carboniferous 

 Limestone may support the waters. 



The saline ingredients may, as at Clifton and at other i3laces, be 

 largely derived from sea-water, or perhaps, as has been suggested, sea- 

 water may have been stored up in the rocks during the vicissitudes 

 or " ups and downs " of past geological periods. 



The question before us, however, is, whence come the saline 

 waters at Swindon? We have mentioned those found elsewhere in 

 the neighbourhood, but before concluding it will be desirable to note 

 very briefly the occurrence of fresh waters in the same area. 



5. Grood supx)lies of fresh water have been obtained in certain 

 localities in JS'orth Wilts, as at Malmesbury and Chippenham. At 

 Malmesbury springs of an artesian character rise in the Abbey 

 meadows from the Forest-marble. These, it is tnie, contain 25 

 grains of solid matter in an imperial gallon ; but the chief 

 constituent is carbonate of lime, with small proportions of sulphate 

 of lime, chloride of sodium, &c. || 



At Chippenham, at Mr. Brotherhood's well, the Cornbrash and 



* Report Brit. Assoc, for 1875, p. 141. See also C. E. De Ranee, " On the 

 Occurrence of Brine in the Coal-measures," Trans. Manchester Geol. See, 

 Dec. 1884 ; and J. M^Murtrie, Proc. Bath Nat. Hist. Chib, vol. vi. p. 84. 



t J. A. Phillips, ' A Treatise on Ore Deposits,' 1884, p. 121. 



\ J. C. Ward, ' Geology of Northern Part of Lake District,' p. 53. 



§ Geology, Chemical and Physical, p. l(j(). 



jl J. H. Taunton, ' Proc. Cotteswold Club,' vol. vi. p. 301. 



