6 The Scottish Natwalist. 



therefore, that the old canoe at Friarton floated on the river Tay 

 at a time when our shores stretched much further out to sea — 

 at a time, indeed, when Britain is beheved to have formed part 

 of the Continent. 



The clay and silt above the peat-bed point to a succeeding 

 period of submergence, when the sea rose upon the land to a 

 height of 30 feet, or thereabout, above its present level. The 

 raised beaches that appear along the sea-coast in Fifeshire and 

 Forfarshire at that height are the representatives of the estuarine 

 clay and silt, which, in the valleys of the Earn and Tay, reach to 

 a somewhat higher level. These latter deposits, which rise to a 

 height sometimes of 20 feet above the old sea-level, bear evidence 

 to former very considerable inundations, when the Tay swelled 

 in flood and covered wide tracts of low ground, depositing upon 

 these its fine mud and loam. At tKat date all the area upon which 

 Perth is built was permanently below water; so that the Tay at 

 Perth was fully a mile in breadth, and the tide must have flowed up 

 to and beyond Stanley. Where the old estuarine flat contracts, we 

 find that the character of its deposits changes ; the clay and silt 

 become more and more mixed up with sand and gravel, until the 

 whole accumulation passes into fluviatile beds of the kind that is 

 most commonly met with along the course of our Scottish streams 

 and rivers. The level of the flat also gradually rises as we follow 

 it up the valley. Thus, in the Carse of Gowrie its upper surface 

 averages about 40 feet or so above the present mean tide. At 

 Perth, its limits are about four or five feet higher, while at Lun- 

 carty it reaches a height of rather more than 50 feet. There is, 

 in short, a gradual passage from marine into estuarine, and from 

 estuarine into fluviatile deposits. 



It is highly probable that when the estuary of the Tay" ex- 

 tended up to Perth, local glaciers existed in many of the upper 

 glens of the Highlands; and I am inclined to think that no in- 

 considerable portion of the fine brick-clays of the second terrace 

 represents the "flour of rocks" formed by the grinding of the 

 glaciers of that period, and carried down by the streams and 

 rivers. These fine clays are overlaid by the loamy silt already 

 described, — a deposit of precisely the same character as the loamy 

 silt which is being carried seawards by the Tay in our own times. 

 Its superposition to the brick- clays would seem to indicate that 

 the snow-fields and glaciers finally disappeared while the second 

 terrace was still covered by the waters of the estuary. 



The brick- clays above the peat-bed contain, as I have said, a 



