174 REV. THOMAS BROWN ON THE OLD RIVER TERRACES 



culty. Our rivers, as we see them at present, flow along a comparatively 

 narrow channel, the greater part of the river valley being usually occupied by 

 level meadows. When a flood comes, it is only the narrow channel that needs 

 to be filled ; and then, should the water rise but a very little over the brim, it 

 will spread out like a sea on either hand. But, after all, it is the banks and 

 meadows which fill the space of the valley. Except in the central channel the 

 sheet of water may be comparatively shallow. And so in that old time the 

 river would have only its central channel lined by banks proportionally higher. 

 The flood would be needed to fill the river bed, flowing perhaps over the brim 

 and out over the surface. In this way these old terraces would be formed just 

 as the present meadows are. The volume of water needed was by no means 

 what would have been required to fill the valley if it had been empty. It would 

 be enough if the confined river bed were filled to overflow. 



But, if things were on such a scale that the river channel was lined with 

 banks 50 or 60 feet in height, where was the water to come from which could 

 rise to such a height ? One explanation has been sought for in the melting of 

 the ice and snow as the glacial epoch passed away. At present, when the ice 

 and snow melt in northern latitudes, the arctic rivers rise annually from 40 to 

 50 feet. This of itself would go a long way to solve the problem. Besides, 

 there was more than the annual melting which takes place at present under 

 ordinary conditions. The fact that the glacial epoch was passing away, must be 

 taken into account. If these terraces may be taken as a record of the time when 

 the great icy covering was melting off the face of the land, and Scotland was 

 passing from the rigour of an arctic climate to its present condition, the currents 

 which filled our valleys may have been increased to an extent which it is diffi- 

 cult to estimate. Swollen lake and flooded river may have risen to a height 

 sufficient to meet all the conditions of the problem we are considering. 



Another explanation which has been suggested, is the existence of a period 

 of great rain-fall — a " pluvial epoch," as it has been named by Mr Tyler. 

 This may have arisen either from the quantity of rain having been increased, or 

 from the rain-fall having been concentrated — a greater amount falling in a 

 given time. Some idea of these floods of the old time may be got from the 

 account of the Moray floods, as given so admirably by Sir Thomas Dick Lauder. 

 They occurred in 1829, and were owing to a fall of rain to the amount of 

 3 1 inches having taken place in twenty-four hours. In regard to the height 

 to which, on that occasion the water rose, the writer mentions having himself 

 seen a man wade into the water and capture a salmon on the haughs 50 feet 

 above the usual level of the Findhorn, pursuing the fish with his umbrella and 

 driving it ashore. The violence and velocity of the currents he describes 

 in striking terms. " It was scarcely possible to follow with the eye the trees 

 and wreck which floated on its surface. The force was as much more than 



