z6o 



DRAINING 



Sect. XL i. 



:> 



under one. In the town of Derby on boring with defign to fink a 



well, 



after having pafTed about thirteen yards through marl, feme 



fand v.as brought up by the auger, and water followed, as related in 

 the Philof. Tranflia. Vol. LXXV. 



The dews therefore, which are perpetually condenfing on the fum- 

 mits of thefe hills, defcend beneath the upper and under ftrata of 

 marl, through the thin flratum of fand, which divides them, and 

 form St. Alkmund*s well, and many other fprings in the vicinity of 



Derby ; and probably all tbofe which fupply the wells Vv ithiu the 

 town. 



r 



manner of the production of 

 )ut a mile from the city of 



B 



th 



fituation. where th 



fprings is mod agreeably vilible ; it is about a rr 



Lichfield, near the cold bath ereded by fir John Floyer, in a beaut 



1 



ful 



sard 



P 



f 



D 



d, which was formerly Dr. D 



hot 



In this place a grotto about fix yards wide and ten long has been 

 excavated on the fide of a hill confiding of filiceous fand-ftone with 

 this' peculiar circumftance ; that the upper dratum of the fand-rock. 



which is there about five feet thick, is divided from 

 turn of it by a flieet of clay not more than three o 

 thick nefs : 



ft 



fo 



on the upper furface of 



flicet of clay, bet 



the 



ps of thefe rocks, a perpetual dribbling of water oozes quite round 



the srotto, like a fh 



& 



from a weeping rock. Such fheets of 



ter having been often obferved to Hide between the drata of 



h 



th almoft horizontally, like the horizontal joints of a ft 



I 



luppofe, given the name of wall-fprings to them, to dift 



guifti them from pipe-fprings, or fuch as burft out in a fingle rill. 



Thus this thin fheet of clay prevents the water from finking ii 



the lower ftratum of fand-ftone ; and produces other copious fprin 



which are colleded at ; 



leaden pipes to the cathedral clofe of Lichfield, which is th 



bout half a mile's diftance, and conveyed 



plied with 



of uncommon purity, which 



fup 



ous 



