180 THE FORESTS OF ENGLAND. 



taking them in historical or ascending order, they run as 

 follows : — First and lowest comes the skull-cap, so called 

 by the quarrymen (whose nomenclature is strictly practical) 

 because it fits tightly just above the Portland building 

 stone. It is a cream-coloured fresh-water limestone, and 

 its thickness is about two feet. Next comes the lower 

 dirt-bed with a few cycads, but no pines. Above this lies 

 • the top-cap, a hard and troublesome bed to clear away, 

 consisting of fresh-water rock with a flinty texture. Then 

 we arrive at the great or upper dirt-bed, a mass of old 

 soil about a foot ' thick, full of cycads and pine stumps, 

 with their roots still firmly fixed in the ground where 

 they grew. Above this again we get the soft burr, or lake 

 sediment, which envelopes and preserves our fossil trunks ; 

 followed by the aish, a slatey lake deposit, the clay 

 parting, the bacon tier, the dirt seam, and last of all the 

 slate, a hard layer some ten or fifteen feet thick, and 

 shivered into small flat pieces about an inch through. 



These are not the remains of woods which have existed 

 within the memory of man ; but the narrative supplies an 

 illustration of what may have taken place in later days. 



Like salecified trees have been found elsewhere in 

 Britain ; but some, if not all of them, appear to have been 

 the products of pre-Adamic times. With the remains of 

 woods now under our consideration, it is otherwise. 



In Denmark, single trees, if not forest clumps, have 

 been found preserved in such situations, as enable the 

 archaeologist to determine by their superposition the suc- 

 cession in which different kinds of trees have grown in 

 the locality, on from the time when the inhabitants made 

 the kocking-middens of shells of molluscs upon which they 

 lived, and used only weapons and implements and orna- 

 ments of stone, to times more fecent — the time of the 

 Roman invasion — and also from that time to the present. 

 And this method of study, which is simple in the extreme, 

 is applicable to such cases as we have had under consider- 

 ation in the preceding section. 



