ON RAINS CAVE, LONGCLIFFE, DERBYSHIRE. 237 



only a small proportion of the stone (the calcium carbonate) has 

 been dissolved, the residue consisting of the double carbonate 

 plus the insoluble earthy matters above alluded to. Now treat 

 this residue with hot acid : the double carbonate is dissolved, the 

 earthy matters remain. The small crystals of dolomite constitute 

 to a very large e.xtent the gritty element of the soil in the vicinity 

 of Rains Cave. 



As might be expected, the relative quantities of the above con- 

 stituents vary considerably in the soil of the cave ; but the 

 insoluble earthy matters are always in great excess compared with 

 those of the mother-rock. Calcium carbonate, too, is always 

 present, perhaps in a stalagmitic form. The following is a fair 

 average analysis of this soil : — 



Calcium carbonate 20 



Calcium-magnesium carbonate 65 



Insoluble earthy residue 15 



100 by weight 



To resume the work of excavation. The discovery of definite 

 bedding modified our procedure, which henceforth consisted in 

 the investigation of the cave floor, layer by layer. The little that 

 remained of the upper two beds right of the datum line, was soon 

 stripped away. This process was repeated on the left side ; but 

 the space on that side, in the posterior half of the cave, being too 

 wide for working conveniently, we divided it into a central and an 

 extreme left region, the one being excavated before the other. 

 The top bed of these regions had no features of special interest. 

 At the end of the cave it was about four feet thick, and consisted 

 almost wholly of loose stones, some so large as to require to be 

 blasted before removal. In one place the stones seemed to be 

 artificially laid, so as to form a rude pavement. 



The underlying bed (C), normally dark and mottled, was the 

 most important in the cave. It varied considerably in thickness, 

 in character, and in the proportionate quantity of bones and 

 objects betokening human presence. It was thickest in the 

 central region, but rarely exceeded six inches where definable ; 



