358 The Scottish Naturalist. 



the shelf whilst a newer is being proceeded with. The newer 

 edition differs from the old only in the fact that it is made up 

 of coarser materials, the natural result of the thousands of years' 

 sortings to which they have been subjected. Countless millions 

 of tons of the finer sediment have been conveyed to the German 

 Ocean, and by this quantity the floor of the valley has been 

 lowered ; and by this same river action the whole of the high 

 haugh may be reduced to a level with the lower haugh, and 

 even to lower still, geographical conditions remaining as they 

 now exist. 



The May, a stream that enters the valley above Forteviot, 

 has distributed an immense layer of pebbles upon the top of 

 the lower haugh.. This pebble bed is therefore higher in 

 position than the pebble beds proper to the lower haugh. 

 This is a natural consequence upon the May descending from 

 the flanks of the Ochils upon the alluvial flat. This stream 

 was without doubt at a higher level, for a bed of pebbles 

 similar to that that it is now placing upon the lower level is 

 found on the top of the higher, 20 feet at least above the 

 present bed. While this small stream has thus reduced its 

 level, has the Earn bed remained stationary? There has been 

 again, either the enormous reduction in the volume of the 

 Earn, or it has reduced its bed in the exact proportion of that 

 of the May. It is the natural province of rivers to scoop out 

 all yielding material, and to carry it away. The Earn valley is 

 filled with detrital matter, most of which was in the valley 

 before the present river ran ; and the river is still at least in 

 many places working into the primaeval clays. 



There is a band of peat in the high haugh forming a zone 

 that possibly represents the mean height of the ancient river. 

 The very presence of the peat would seem to suggest, that 

 even low water mark was not much beneath its zone. Here 

 once more we have the necessity for the swollen state of the 

 Earn to have been constantly maintained for a very long period. 

 Such an exceptional condition of the river is hardly likely to 

 have been so constant, but if we more naturally place our 

 stream at a higher level, it has but to reduce its bed one 

 foot in a thousand years or less, and there is ample time for 

 all that it has done to have been accomplished. 



To conceive that any river can wear and tear away its 

 surroundings, and come down annually, laden with mountain 

 masses in a pulverised condition, and thus act for thousands of 



