Sharp — On a Singular Incrustation, 565 



course of time, was choked np, becoming at length only a shallow 

 puddle. The six inches of calcareous paste at the bottom was pro- 

 bably produced by the crushing of the lower portion of the incrus- 

 tation by the superincumbent weight ; and the thick layer at top, 

 partly by atmospheric disintegration, and partly, perhaps, by the 

 trampling of cattle while drinking. The pool ultimately became a 

 mere marshy hollow, and was then artificially filled in with soil to 

 the level of the surrounding surface. The gravel-pit was subse- 

 quently opened, and what had been the hollow of the pool was thus 

 thoroughly drained. 



The incrustation lies in layers, the plant stems being in a greatly 

 inclined position. I would suggest that this may, perhaps, be at- 

 tributable to the deciduousness of the plant, or to the variation in 

 the water-level arising from the change of seasons. 



There is one peculiarity which I must notice. The gravel-pit is 

 situated on the slope of a rather shallow valley, through which flows 

 the brook I have referred to. The bottom of the pit is some feet 

 above the level of the water of that brook, and about three feet below 

 the bottom of the supposed former pool : at a time of the year when 

 water should have been present, if at all, the pit was perfectly dry. 

 It is clear, then, that the old local conditions must have been very 

 different to the present, to have rendered it possible for water to 

 accumulate in an excavation in that open gravel to such an extent as 

 to allow of the Chara growing in luxuriance to within a foot of the 

 surface. It would really seem that, in the long interval which has 

 elapsed since the growth and incrustation of that mass of plant, a 

 change must have taken place in the level of the locality, and that 

 the valley itself must have been excavated to a greater depth. If 

 this view be sound, and the pool or hollow be really the work of 

 man's hands, we have here another item of evidence of the high 

 antiquity of the human race.^ 



There is yet another consideration. Had the gravel pit not been 

 opened, the calcareous paste of the upper bed would, by percolation, 

 in the course of time, have completely filled up the interstices of the 

 mass of incrusted plant, and ultimately the whole might have become 

 hardened into a marly limestone rock. If excavation should then 

 have occurred, what would have been the reasonable conclusion as to 

 the nature and origin of the apparently calcareous mass ? Would it 

 not have been that, occurring in the stratified gravel, it was a trans- 

 ported block, and its presence in such a position attributable to 

 Glacial agency ?^ 



1 Mr. George Maw, F.G.S., etc., upon the facts as detailed by the writer of the 

 paper, has expressed an opinion (qualified by the consideration that he has not 

 examined the place) that the hollow was the work of human agency. 



2 The valley is cut through the lower beds of the ferruginous sandstone of the dis- 

 trict ; upon the slope so formed the gravel was deposited, and the ferruginous sand- 

 stone reposes upon the upper Lias clay. Neither of these beds contain suflficient cal- 

 careous' matter to allow of any subsidence arising from the dissolving out and carrying 

 away (by the action of water charged with carbonic acid in solution), of any consider- 

 able portion of their mass. 



