520 E. Wilson — Sections in Tideswell Dale. 



also near Silverdale, are many conical and dry pits in G-lacial drift, 

 where the subjacent strata are undoubtedly calcareous and frequently 

 pierced by swallow-holes. 



It is worth while to separate the two sorts of excavations which 

 have been described. They are locally known as "buttertubs" and 

 " pots." If it be necessary to find terms more precise and dignified, 

 they may be distinguished as " cavities of erosion " and " cavities of 

 subsidence." 



VI. — Altered Clay-bed and Sections in Tideswell Dale, 

 Deebyshiee.^ 



SiE, — The Geological Magazine for August, p. 394, contains 

 a report of a paper communicated by the Eev. J. M. Mello to the 

 Geological Society, on the 22nd June, 1870, on the above subject. 

 On the 7th September, 1869, I had the honour to read a paper on 

 the same subject to the Natural Science Section of the Nottingham 

 Literary and Philosophical Society. Hence I beg to claim priority 

 in publication on behalf of the above Society. Apart from this, 

 I, of course, do not complain that Mr. Mello should happen to select 

 a very interesting section like that in TidesweU Dale, no doubt being 

 quite unaware that I had already published an account of the same. 

 The sole, though rather dubious, deduction that the author is reported 

 to have made, is " that the columnar clay-bed may perhaps be a 

 local development of that which forms partings in the limestone 

 near Litton Tunnel." In my paper (extracts of which I inclose) I 

 endeavoured to account for the clay-bed, or rather mass, in another 

 way, and was at some pains to prove, or to try to prove, that the 

 bed in question was not a thickened clay parting, much less a series 

 of partings. I do not know whether Mr. Mello's paper is correctly 

 represented by the very brief account you give, but the Section was 

 of opinion that my paper deserved a full report. 



I was so much interested in what I saw in one day's trip that I 

 determined to visit the district again and examine the igneous rocks 

 of the Derbyshire Carboniferous Limestone more thoroughly. The 

 opportunity has not again occurred. I can, however, conscientiously 

 recommend the task to those of your readers who are conveniently 

 situated for the purpose or who have time at their disposal. 



Edwaed Wilson. 

 Hall Street, Sher-wood, Notts., 10 Aug., 1870. 



" On the west side of the Dale (TidesweU), at the same level as, 

 and almost directly opposite the marble quarry, I found a very 

 curiously filled up cavity in the limestone, exposed in the cutting 

 of the road along the hill-side. At the base limestone, highly fossil- 

 iferous beds, two to three feet thick, minor joints confined to single 

 beds ; above lies an apparently imperfectly laminated band of yel- 

 lowish clay, which, at one or two places, dips down into, and fills up, 



' The publication of this communication has been unavoidably delayed from want 

 of space. 



