and Forest-beds in Cornwall. 133 



Such an idea would postulate the entire desertion of the main 

 drainage lines during the period of forest growth, of the duration of 

 which the Forest-bed in stream-tin sections affords no measure 

 whatsoever. 



Take for example the Happy Union Valley. Part of it was at least 

 tenanted by running water, the old forest-bed (to use a relative 

 term) being buried beneath a stratum of silt, probably river detritus, 

 one foot thick; then we have a nearly continuous layer of vegetable 

 matter, probably drifted, and an appearance of silting up and of 

 moss growth, the water being confined to small runlets hardly 

 breaking the continuity of vegetable matter. After this the gradual 

 prevalence of estuarine conditions is evidenced in a bed of silt, 

 which resembles, from the description, as Mi*. Greikie points out, 

 the bluish clay so often found beneath the submerged forests on 

 the foreshore. In this silt drift-wood also occurs ; but as the top of 

 the bed is about 18 feet below low-water level, it would have been, 

 supposing the growth in situ, subjected to estuarine conditions before 

 the forest belt on the foreshore was buried beneath sea sand ; 

 and the vegetable matter corresponding strictly in position with the 

 submerged forest between high- and low-water mark would, as Mr. 

 Greikie points out, occur in the bed of sand 20 feet thick, in which 

 oaks were found lying in all directions, and bones of red-deer, etc. 



In Carnon Stream Works, as given by Mr. Henwood (T.R.G.S. 

 Corn. vol. iv.), where human remains were found in association with 

 vegetable matter at 46 feet below low-water, there would appear to 

 be no vegetable representative of the forest growth on the foreshore : 

 but 1 cannot therefore regard the vegetable bed on the tin ground in 

 this section as representing an older land surface than the submerged 

 forests fringing the coast-line, in any other sense than its position in 

 a depression entitles us to infer — that its growth as a tiny portion of 

 a large forest tract was of less duration than that of portions not 

 similarly situated, and being submerged before the districts at a 

 higher level did not remain a land-surface so long. 



The growth of woods on the tin ground soil would be unlikely to 

 lead to the formation of a bluish-grey substratum, such as we find 

 beneath most traces of submerged vegetation on the coasts, resulting 

 from surface decomposition of the Killas, tinged by carbonaceous 

 matter; so that such differences are no doubt due to the accidents 

 of position. Local conditions, however, were so varied as to permit 

 of the formation of a clay soil in certain valleys, Pentuan for 

 example, upon alluvial deposits accumulated subsequently to the 

 destruction of the parts of the forest rooted in the tin ground, and 

 this clay appears to be similar to that which we find beneath those 

 portions of the submerged forest between high- and low-watermark, 

 which doubtless nourished the forestial growth from its beginning 

 to its close over much of the area it originally occupied. 



The expression "older land-surface," as indicated by the forest- 

 bed on tin gravels, has been fully explained to me by Mr. Geikie, 

 who kindly furnished me with the following summary of his views, 

 thereby depriving these remarks of any controversial character. 



