POST-TERTIARY FOSSILIFEROUS DEPOSITS. 



81 



3. Peat with remains of trees. 



4. Carse-clay with bones of Whale. 



5. Peat, with roots of oak trees at the bottom and remains of an old wooden road. 



The peat (3) is described as a " land-surface of the period preceding the deposition 

 of the old estuarine mud," and commented upon as follows — " This bed of peat, lying 

 beneath the raised estuarine beds, is the first appearance of that substance we meet 

 with in Scotland ; indeed the period during which peat was formed so extensively from 

 the gradual accumulation of mosses, sedges, and various other plants, is, perhaps, even a 

 stage later ; for at the bottom of many of our peat-mosses we find remains of trees and, 

 in some cases, beds of shell-marl. These trees are all of existing species now indigenous 

 to Scotland. The birch, hazel, and oak are amongst the most common, and hazel nuts 

 are frequently found. Now these trees testify, I think, to a condition more favorable to 

 the growth of loood than what loe have at present. They evidently preceded the com- 

 mencement of the peat in a multitude of instances, for their roots are spread on the hard 

 earthy soil beneath it, and it is since the death of those trees that many of our peat- 

 mosses date." 1 



Evidence is also brought to show that the remains of trees are now found in Scotland 

 " at heights beyond where wood can now be got to grow." " 



2. COLINTRAIVE, KyLES OF BUTE. 



Following the Loch Ridden Road on the Colintraive side of the Kyles of Bute, in a 

 small bay, about a quarter of a mile from the pier, a shell-bed is exposed at low-tide 

 which has been confounded with the true glacial clay, but which certainly belongs to a 

 very different age. In this deposit Pecten maximus and Ostrea edulis occur, of enormous 

 size, associated with Aporrhais pes-pelicani, Lutraria ellijjtica, Psammohia Ferroensis, 

 Lucinopsis undaia, Tellina squalida, all British species, but constituting a group of shells 

 which could not now be obtained in the same abundance and perfection in the imme- 

 diately neighbouring waters of the Kyles. 



It is true that the partial or total disappearance of shells on particular banks depends, 

 in a large measure, on local circumstances, which may be of comparatively recent 

 occurrence. It is not unusual when dredging to find banks, at various depths, covered 

 with old dead shells, without a living one of the same species among them. In the bay 

 at the head of West Tarbert Loch, a little below high- water, on digging through a foot of 

 sand, a bed of sandy mud was reached, with large specimens of Scrobicularia piperata, 



' Ibid., p. 186. 2 Ibid., p. 187. 



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