388 PREHISTORIC EUROPE. 



occasional large erratics, floated out to sea, and now and again 

 dropped their burdens on the way. No trace of land-plants or 

 land-animals has yet been met with in these ancient estuary- 

 deposits, as we may be sure they would have been had either 

 abounded. The intensely arctic character of the marine fauna, 

 the common occurrence of ice-floated stones and boulders, the 

 tumultuous aspect of the flood-gravel and shingle of the swollen 

 torrents which poured into the estuary on every side, all testify 

 strongly to the severity of the climate. The upper reaches of 

 the estuary must have been greatly freshened by the influx of 

 ice-cold water, and that is perhaps the reason why no marine 

 organic remains occur in the estuarine deposits above Errol. 

 We must not forget, however, that over wide areas the deposits 

 in question are concealed under newer accumulations, and were 

 they better exposed to observation they might possibly be found 

 to contain a more abundant fauna than they have yet yielded. 



i Such, then, appear to have been the conditions under which 

 the late glacial deposits of the Tay and the Earn were accumu- 

 lated. They are contemporaneous with the great kames and 

 gravel-flats which cover extensive areas in the low grounds that 

 sweep up to the base of the Grampians. A gradual passage can 

 be traced from the true estuarine beds into flood-gravels of 

 fluviatile and torrential origin, and these latter are closely 

 associated with coarse shingle, and rounded boulders, and earthy 

 ddbris, and angular erratics, which cumber the lower reaches of 

 the mountain -valleys, where they assume the form of true 

 moraines. The last continuous ice-sheet had melted away from 

 the low grounds, and the glaciers which still occupied the 

 mountain-valleys were gradually retreating under the growing 

 influence of milder climatic conditions. 



3. The beds which immediately overlie the late glacial 

 deposits of the Tay and Earn carry us with a leap into a very 

 different condition of things. They consist of river-gravel, sand, 

 and silt, and rest upon a highly denuded surface of the older 

 deposits. As a rule the sand and gravel are clean and not 

 commingled with clay, and here and there they show false- 



