E. Wilson — Sections in Tideswell Dale. 521 



the space between the jointed limestone blocks. Into the largest of 

 these clay-lined basins is protruded a tongue of vesicular toadstone (im- 

 perfectly columnar), and one side of the toadstone tongue is coated 

 with a thickish mass of red clay, identical in texture with that found 

 in the marble quarry (Fig. 2) and the district generally (see Fig. 1). 



Fig. 1. Section in Tideswell Dxle opposite the Quaret. 



7. Siirface soil. 



6. Toadstone amorphous in B, slightly vesicular in A. 

 5. Vesicular do. a. Carhoniferous Limestone. 



4. AmygdaloidsB 1 do. a'. Boulders of do. in surface soil. 



3. Scoriaceous do. 



2. Ked clay mass 2a! (Fig. 2) columnar portion. 



1. Ash decomposed and rearranged, yellow friable argillaceous layers. 

 N.B. — The figures in both sections correspond. Fig. 1 has really a semicircular outline, like 

 a small amphitheatre, but is represented as if it had a plane surface hke Fig. 2. 



Height of section 12ft, length 20ft. I hazarded the conjecture 

 that the cavity was a natural irregularity in the Carboniferous Lime- 

 stone sea bottom, that a volcanic eruption ensued, preceded by showers 

 of ashes, that these latter sank, and being arranged by marine currents 

 would naturally accumulate in the hollow, the eruption continued, a 

 mud flow next ensued (the so-called red clay), just as rivers of mud 

 have poured in modem times from Vesuvius, the volcanoes of 

 Java, etc- This succeeded in forcing itself into the basins of ashy 

 matter, and was in turn succeeded by the true, probably chiefly 

 if not entirely submarine, lava (or toadstone) flow (or flows), which, 

 on account of its greater density, forced a passage for itself, be- 

 tween the plastic clay and ash, as shown in the section, before 

 hardening. Crossing the Dale we inspected the quarry. The base 

 there was also compact horizontal coralline marble, about 6ft. ex- 

 posed. Directly above comes a mass of deep red clay, 8ft., compact 

 below, but in its upper portion taking on a very distinct columnar 

 structure, the columns varying from 4 to 6 feet in length, and 

 showing, in cross section, square pentagonal and irregular hexago- 

 nal forms. It appeared at first glance, on entering the quarry, as 

 if a number of men had been working with the pickaxe in soft 

 clay. Closer inspection, however, shows the regularity and a certain 

 duplex contortion of the columns (see Fig. 2). 



This band has not the slightest trace of lamination either in 

 the columnar or non-columnar portion, but, on the contrary, is ir- 

 regularly veined and streaked with a softer greenish-white scaly 

 material, apparently of a chloritic or talcose nature. Above this lies a 

 considerable mass of toadstone, which consists in ascending order of — 



3. Scoriaceous band, dark earthy and porous ft. 4 in. 



4. Toadstone amygdaloidal blending into ft. 2 in. 



5. Toadstone vesicular blending into ft. 8 in. 



6. Toadstone amorphous basalt to surface (about), 16 ft. in. 

 (the total thickness when undenuded must exceed 60 ft.) 



