90 Tlli; KKV. G. K. HALL, F.S.A., 



but it appears that a quai-ter of an inch or rather more was noticed 

 upon the sliders nearer to the bottom of the pit-shaft. Many of 

 these are not yet removed. On the outer side next to the strata 

 the calc -sinter'^' is thicker than on the inner side which was sub- 

 ject to friction from the cage ; and there the lines of diip and 

 shallow vertical grooves are observable, with tiny bosses of drip- 

 stone, the whole suiiace sparkling in favourable lights. Thi'ough 

 the fissures in the superincumbent strata the drops have perco- 

 lated slowly down the timber cage-supports, and the bi-carbonate 

 of limef held in solution therein has re-assumed its crystalline 

 form, the excess of free carbonic acid being yielded up to the air 

 through exposure to the air-currents and evaporation. The sur- 

 face of the timber, wherever it has been bathed by the thin films 

 of the liquid, impregnated by the salt of lime, has become a sheet 

 of sparry deposit having on the under side a beautiful and exact 

 representation of every fibre and knot of the wood. 



The inner side of the boards next the shaft shows at once the 

 marks of friction from the frequently-descending '' cage," which 

 has prevented the encrustation being formed to the same thick- 

 ness as on the other side. 



It is a point of considerable interest, both in its geological and 

 archa}ological aspect, to ascertain any facts that may throw light 

 upon the rate at which stalagmite has been and is being formed. 

 I have pre\4ouslyJ had occasion to refer to one instance that has 

 occurred within the range of our Society's operations, that is, at 

 Boltsburn, in Weardale, where, as the case is given in H'ature,^ 

 three-quarters of an inch of ciystalline stalagmite had formed on 

 boards, which liad, in connection with a lead-mine, been placed 

 there just fifteen years previous. But a much stronger instance 



• Lat. calx, calrin, llmo, nnd Oor. sintern, to drop. Professor Pajfc, LL.U., F.0.8, iu 

 Ills vnlualtlc "Advanced Tcxl-UiM>k of Gcolotry," i>tl> Edit. (Glossary) p. 4ol, remarks, 

 "Thin torm U Dkually applied to compact stalaginitical or ntalactitical doiwsits from cal- 

 careous waters. The uTadual increment of calc-sintcr is usually marked by linos or layers 

 of varying ImrdncHS and colour." 



t "The Ancient Stone Implements, etc., of Great Uritain," by John Evans, F H.S., 

 I.H.A.. Chap. XXII., p. 431. 



% rresidentinl Address, Vol. V. (New Scries), Part III , .'<;<:. 



fi December 18th, 1873, p. Wi. 



