The Scottish Naturalist. 3 



does not average more than 12 or 14 feet above mean-tide 

 mark. Here and there along the course of the river there are 

 patches of alluvium at lower levels, but these are all of very 

 recent formation, and need not at present be considered. The 

 deposits of which the first terrace is composed consist of silt, 

 sand, and gravel. 



The second terrace is not less well marked than the first. The 

 latter cuts into it, as it were, so as to form a more or less con- 

 spicuous bank. Thus the lower flat is almost everywhere 

 bounded by the truncated edge of the second terrace. The 

 upper surface of this second flat rises from 25 feet or so, up to 

 45 feet or thereabout. At many places, however, where it 

 abuts upon the lower terrace, its surface is as much as 10 or 

 12 feet above the latter. In the immediate neighbourhood of 

 the city its average level cannot be less than 38 or 40 feet 

 above the sea. 



The highest terrace in the vicinity of Perth is not so well 

 marked as either of the lower flats. It ranges from 50 to 90 feet 

 in height above the sea. But it has evidently suffered extreme 

 denudation, so that its terrace-like aspect is conspicuous only 

 here and there. It is composed for the most part of sand and 

 gravel, but now and again is largely made up of fine clay. 



The deposits at Friarton Brick-works belong to the second 

 terrace, and are of a fluviatile or estuarine character. The 

 lowest beds consist, as we have seen, of gravel and sand. The 

 only fossils that I have met with at this horizon are fragments 

 of land-plants, and these occurred in the sand. Some of them 

 appeared to be roots, others were twigs which had evidently 

 been floated from some little distance. The sand, however, 

 as a rule, is unfossiliferous. The bed described as peat is 

 of variable thickness. It consists of a mass of vegetable matter 

 — the principal or most conspicuous components of which are 

 the leaves and stems of reeds. The peat is considerably com- 

 pressed, and splits up into laminae, on the surface of which 

 many small seeds may sometimes be detected. Amongst the 

 vegetable debris twigs and fragments of pine are not uncom- 

 mon, and now and again bits of birch may be detected. But 

 the whole is so much decomposed that the original character of 

 the vegetation is not easily made out. Lying upon and in the 

 peat, and sometimes partly penetrating the sand below, occur 

 mow and again trunks of trees, which have all the appearance of 

 having been drifted into their present positions. Many of these 



