236 ON RAINS CAVE, LONGCLIFFE, DERBYSHIRE. 



representing as on one vertical plane what in reality were hori- 

 zontally separated. The line H, H, H^ represents the extent 

 downwards of our diggings, mostly in the right region; H' repre- 

 sents a part of the external inclined trench. We found that almost 

 from the first we had unconsciously made acquaintance with all 

 these beds, and it accounted in great measure for the widely 

 different results of the foot-strips. The top bed (D), with its 

 seams of stalagmite and hearth, has been sufficiently described for 

 the present. Before dealing with the rest, it is well to point out 

 wherein they all agree. With about only a dozen exceptions — 

 and most of these clearly imply human agency — all the stones 

 contained in these beds were derived from the parent rock 

 (dunstone) of the cave. They were all angular or sub-angular ; 

 none were water-rolled, or took the shape of boulders. The loam, 

 whether fine or coarse, whether approximating to a clay or to 

 sand, had also the same source. To this loam we will devote a 

 few minutes. 



In general character it was identical with the sub-soil of the 

 district — a fawn-coloured, more or less gritty calcareous loam, 

 derived from the disintegration of the bed-rock, a dolomitized 

 carboniferous limestone, commonly known as dunstone. The 

 normal limestone of this formation consists of calcium carbonate, 

 with a variable but always small percentage of earthy matters 

 insoluble in water charged with carbonic acid, as all terrestrial 

 water is. These earthy residues alone, or to a very large extent, 

 form the true cave-earths of caves excavated out of this rock, and 

 generally they largely contribute to soils derived from it. They 

 exist in dunstone, but play only a comparatively small part in the 

 products of its disintegration. This is owing to the less solvent 

 quality of the magnesium-calcium carbonate (dolomite), of which 

 this rock is so largely built up, compared with that of simple 

 calcium carbonate. The action of natural water [i.e., water 

 charged with carbonic acid) may be illustrated by that of diluted 

 hydrochloric acid. If some dunstone is treated with this acid, 

 there is a brisk effervescence, which, however, soon subsides, or 

 nearly so. If the residue is dried and weighed, it is found that 



