394 PREHISTORIC EUROPE. 



was a native of the land, and in his rude canoes, dug out of 

 great pines, boated up and down in the ancient Tay. 



5. Deposits of clay and silt — the so-called Carse-clays — im- 

 mediately overlie the old forest-bed, and vary from ten or fifteen 

 feet up to fully forty feet in thickness. In a few places the 

 beds which directly cover the buried forest consist of gravel and 

 sand ; these, however, are almost invariably overlaid with thick 

 accumulations of clay, silt, and loam. 



The surface of these deposits, which form the greater portion 

 of the Carse of Tay and the flats of the Earn valley, is usually 

 stated to be about 25 or 30 feet above the sea; but this is rather 

 the minimum than the maximum. Only a small area is under 

 30 feet ; indeed the mean level between Monorgan and Errol 

 can hardly be less than 32 feet. From the railway to the foot of 

 the Sidlaw Hills, against which the Carse-lands abut, the ground 

 rises with a very gentle gradient, so as to attain a height at the 

 margin of the Carse of not less than 45 feet. Thus a wide district 

 between Errol and the Braes of Gowrie averages more than 40 

 feet above the sea. The boundary of the Carse, followed along 

 the foot of the hills from Longforgan up to and even beyond 

 Perth, is as near as may be horizontal and persistently 45 feet 

 in height. Above Perth it gradually merges with old river- 

 terraces of silt, sand, gravel, and shingle. The wide flats in the 

 lower reaches of the Earn valley are merely a continuation of 

 those of the Carse of Gowrie, with which they correspond pre- 

 cisely in elevation. A considerable part of the flats of the Earn, 

 like much of the Carse of Gowrie, does not average more than 

 32 feet above sea-level, but in many places it exceeds 40 feet. 

 The upper margin of the Earn flats is also approximately hori- 

 zontal, and continues at an elevation of 45 feet as far inland 

 as Dalreoch, beyond which it shortly passes into true river- 

 alluvia. 



Such facts suffice to show that these upper deposits of the 

 Carse are of estuarine origin, and their connection with a former 

 lower level of the land, and consequent incursion of the sea, is 

 demonstrated by the appearance of marine shells in the clays. 



