50 ANNALS OF SCOTTISH NATURAL HISTORY 



and the very coarse sand and gravel with which they are 

 associated ; and then followed the vegetable soil, and now 

 the quarry. 



II. The Arctic plant-beds and other beds in Corstorphine Lake. 



This lake lay in the hollow that stretches along the 

 south side of Corstorphine Hill, from Coltbridge to west of 

 Corstorphine village, a distance of 3 miles or more. The 

 deposits in it were exposed in 1890-93 by a cutting for a 

 sewer in connection with the Water of Leith Purification 

 Scheme. This cutting was about 20 feet in depth, and 5 

 feet in width ; and all the beds that lay in its course were 

 exposed to that depth. The cutting may be treated in 

 three parts or divisions. 



1. From Coltbridge to Ballgreen Road, about a mile. 

 This was the lowest level, and the beds in it were wholly 

 mud or sand, with intercalated beds of vegetable drift or 

 compressed peats. All the organic remains from it were 

 recent, such as hazel nuts, acorns, seeds, pieces of driftwood 

 of pine or oak, and bones of the pig or ox, etc. 



2. From Ballgreen Road westward to the Corstorphine 

 Station Road, nearly two miles in length, the chief beds 

 were lake-marls full of freshwater shells. The thickness of 

 these beds was sometimes only 2 or 3 feet, but at other 

 places it reached 20 feet or more. Next came the Arctic 

 plant-bed, in fine lake-mud of varying thickness, sometimes 

 only one inch in thickness, sometimes a foot or more. In 

 some places it lay within six or seven feet of the surface, 

 at others it went down to the bottom of the cutting. It lay 

 in some places on laminated clay, in others on a coarse gray 

 sand. 



3. Above the Station Road, as far as South Gyle, for 

 about a mile the marl alone was cut into, as the cutting was 

 there only 12 or 14 feet in depth. The marl was the same 

 as in section 2, full of freshwater shells and flat stems of 

 water-plants, evidently representing the later stage of the 

 lake's history. Probably if the cutting had been deeper the 

 Arctic plant-bed would have been found below the marl here 

 likewise. 



