96 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 8, 



Passing southward over the ridge, and at a point immediately below 

 its summit, the upper beds of this sandstone series are observed, 

 underlying and passing into the Carboniferous Limestone series 

 above. 



This junction with the superincumbent limestone beds is clearly 

 to be seen in a quarry S. of the road, in a line with the one we 

 have been describing. The general relations of the series are seen in 

 the following section. The strata dipping to the S.E. at an angle 

 of 60°. . 



All the beds in this section, and more especially the oolitic lime- 

 .stone, are seen to increase in thickness as we trace them eastward 

 from Farlow to Oreton. 



Many Cestraciont palatal teeth and Brachiopodous shells have 

 been obtained from this opening into the limestone ridge, so graphi- 

 cally described by Murchison. Half-a-mile eastward of it are the 

 greater quarries of Oreton. There is evidence in the intermediate 

 space of the limestone having been formerly worked ; for numerous 

 hollows, from which stone has been got, make the irregularly 

 undulating ground still more uneven. 



We are indebted to the Eev. J. Williams, of Farlow, for some 

 valuable information relating to a recent exposure, in one of the 

 deepest of the Oreton quarries, of the subterranean stream w^hich 

 has long been known as flowing parallel with the axis of the ridge. 

 This " mole river " loses itself in a hollow called the Foxholes, at the 

 western extremity of the limestone, and, taking an N.N.E. course, 

 reappears at the distance of a mile, about 300 yards from its con- 

 fluence with the Eiver Kea. Two of the quarrymen, who had struck 

 upon it at the depth of about fifty feet from the surface, described 

 it as a constant stream, occasionally greatly swollen by floods. An 

 interesting account of an accidental stoppage at its inlet during one 

 of the great floods of last year was furnished us by Mr. Williams. 

 He stated, from his own observation, that two and a half acres of the 

 hollow were covered to an average depth of fifteen feet by the dam- 

 ming up of its course. Forty-eight hours sufficed to drain away this 

 accumulation of water through its underground passage. From the 

 data supplied by the careful observations of Mr. Williams, whose 

 residence is above the stream, the lake thus formed must have con- 

 tained one million six hundred and thirty-five thousand cubic feet 

 of water ; and the rate of its subsidence was not less than thirty- 

 four thousand cubic feet per hour. It appears from this that the 

 fissure through which the stream flows is of no insignificant dimen- 

 sions. 



§ 3. The quarries at Oreton are very extensively worked, and 

 afford a good section of the general thickness and character of this 

 Umcstone in its northern area. In the order of the beds, the deposits 

 are a repetition, in greater thickness, of those exposed at Farlow. The 

 variable character of this limestone, and its thinning out at each 

 extremity, have been alluded to in ' The Silurian System,' and are 

 interesting as showing the different conditions, within a limited 

 area, which obtained during its deposition. As a rule, the middle 



