OF THE EARN AND TEITH. 153 



below Ochtertyre, I found the same three levels in still more striking propor- 

 tions, and it at once became a question how far they could be continuously 

 traced along these river valleys. 



Beginning at the foot of Glenartney there could be no doubt as to the lowest 

 level forming the present banks of the river. It passes downwards and spreads 

 out into extensive meadows. And equally marked was the extension of the 

 second terrace, the steep escarpment of which goes sweeping for miles, forming 

 a great irregular triangle from Cultibregan to Lennoch, the level flatness of the 

 surface being not less remarkable than that of the Carse lands at Bridge of Earn. 

 The highest terrace, however, is often discontinued, especially along the right 

 bank of the river ; but away to the north, beginning at Coneyhill, portions of it 

 may be seen at Tomperran, Lawers, and especially at Monzievaird. It soon 

 became apparent that these terraces were a good deal interrupted, appearing 

 and disappearing by turns, while at intervals the threefold system is in full 

 preservation. But these interruptions are not to be wondered at, when we 

 think of the denuding agencies to which the deposits were exposed. The 

 loose sands and gravels, of which they were composed, were just the materials 

 most liable to be washed away, and their position on the sloping sides of the 

 valleys was precisely that on which the denuding agencies would most power- 

 fully act. It is plain also, that the rains and floods of the old time were much 

 more powerful than now, and, if we picture them to ourselves, rising to a height 

 and acting with a force to which nothing at the present day can be compared, 

 it is little wonder that the terraces have in many places been removed, and in 

 others greatly worn down and obscured. 



Making fair allowance for all this, it became a question, whether anything 

 like a continuous chain of these deposits could be traced along the course of 

 the valley. During the autumn of 1865, and again in 1866, I had some weeks 

 of leisure on my hands, and I thought something might be done to ascertain 

 the point. Taking the Ordnance Survey map in my hand, I filled in as I went 

 along the results of my observations, using a separate colour to mark each of 

 the three levels. At all points of importance I endeavoured to ascertain, from 

 actual sections, the internal structure of the terraces, for there is always a risk 

 of mistaking for a terrace what is really due to the rocky structure of the 

 country. I took also a series of measurements showing the height of the 

 deposits above the river course ; but being alone I had to content myself with 

 only approximate results. Thus, I followed the Earn, from where it leaves the 

 loch to where it meets the tide, through many pleasant days, amidst scenes of 

 quiet river-side beauty, which I shall not soon forget. The results are given 

 in the accompanying map (Plate IV.) That I have succeeded in all cases 

 in reading the deposits aright, or in tracing their boundaries, is, I am afraid, 

 more than I can hope for. I offer it merely as an approximative eye-sketch, 



VOL. XXVI. PART I. 2S 



