316 The Scottish Naturalist. 



The point now reached is the extreme western end of the 

 map (Plate III). So far I had been uncertain of the origin of 

 this higher haugh although the truth had begun to dawn. I 

 proceeded from this spot to about a quarter of a mile higher 

 up where the High Haugh pushes the river into a narrow limit 

 on the north side of the valley at a point below Dupplin, whence 

 it (the haugh) suddenly deflects in a grand curve to the extreme 

 south side of the alluvial plain towards Forteviot, so that it forms 

 a promontory upon the lower level. 



Here the section is a sudden contrast to all that has hitherto- 

 been seen. The upper portion is clay like that before noticed, 

 but there is evidence of its having been denuded from above. 

 The vegetable zone is also seen, but somewhat meagrely. The 

 sand bed is almost altogether absent, and gives place to an im- 

 mense bed of well -rolled pebbles similar in every respect to- 

 those that form the pebble accumulations of the lower haugh. 

 This pebble bed is so impregnated with iron that it is an almost 

 solid mass, and has proved an impediment to the denudation 

 of this portion of the upper haugh of which it is a part. For 

 this reason the river has remained pent up within the nase and 

 the high-lying ground on the north, whilst in other parts it has 

 gone from side to side of the valley over and over again. The 

 river has done its best to bring down the barrier, having eaten 

 away all the High Haugh where the low track occupies the 

 valley both above and below. It has even repeatedly during 

 spates rushed over it, denuding its upper stratum of clay. But 

 it has resisted all attacks, and remains to make clear the High 

 Haugh's origin. 



In order to appreciate a part — I may not, perhaps, say all — of 

 what we have seen in our valley, of the river and its mode of de- 

 nudation, of the pebble-beds of the lower and the higher Haughs, 

 and of their respective strata, we must take our backward way 

 among the years — the wondrous, nameless years — that hold our 

 world's great history. Yet, as we have to deal only with the 

 valley of the Earn, we need not scour the earth from end to 

 end, but just turn over one short page, and read the closing 

 lines of the pre-historic record. This will take us back to a 

 period when the British Islands were bound beneath the hand 

 of a continuous winter — when, higher than the mountains, glis- 

 tened the eternal ice — when every group of hills became a 

 centre from which the glaciers crept adown the valleys and 

 across the plain with never-ceasing progress to the sea. These 



