86 Transactions. — Miscellaneous. 



A still more remarkable result of the flood was presented in connection with 

 the lateral valleys which opened on to the terrace of the main river. You 

 will remember that I described the front line of each of these valleys, drawn 

 from the extremities of the bounding spurs, as presenting the appearance 

 of an ordinary river terrace, more or less deeply cut through by its own 

 particular stream, and I mentioned that each of these streams had formed, 

 at its debouchure on to the surface of the main terrace, a half-cone of 

 detritus over which it continued to flow, or through which it had cut a 

 channel more or less deep as the case might be. Now, before the flood of 

 1868, there was not, in any instance, more than one such half-cone in 

 connection with any one valley, the stream from each valley having unques- 

 tionably debouched from the same channel on to the main terrace ever 

 since the waters of the main river had ceased to run at the level of the 

 upper surface of that terrace. But in the case of several of these larger 

 lateral valleys, the channels of their streams, though wide and deep, had 

 proved to be entkely insufficient to carry off the enormous quantity of 

 water which had suddenly poured into them during this flood, the con- 

 sequence being that the surplus water overflowed the valley and found 

 its way along one or more lower lines on its surface over the edge of its 

 frontal-terrace on to the main terrace below. These valley-terraces are, as 

 I think I have before observed, composed of loose gravels and silt. Now 

 the quantity of surplus water was so great in some instances, that wide 

 fresh channels were cut through the fronts of the valley-terraces, and fresh 

 half-cones deposited on the main terrace below, some of them being actually 

 larger than the old half- cones which had accumulated in front of the 

 original debouchures during the immense time which had elapsed since 

 they began to be deposited. There could be no mistake about this opera- 

 tion. There were the large open gaps freshly cut through the front 

 terraces, in some instances extending in depth to the sohd rock below. 

 There were the great new half-cones, some of them covering several acres of 

 the previously level surface of the main terrace, and formed out of the 

 materials which had filled these gaps. But no water has ever since flowed 

 through these new gaps. The streams of the lateral valleys are again 

 flowing in their old channels, and the latter have, in almost every instance, 

 been emptied of every atom of the loose material which had previously lain 

 in their beds, thus giving largely increased room for the flow of the water. 

 Chasms along the line of these streams, in their course across the main 

 terrace, in some instances ten and twelve feet deep, the bottoms and sides of 

 which are clean solid rock, have taken the place of beds of shingle which had 

 formerly filled them up to the general level of the ground, the consequence 

 being that ^ considerable number of bridges have had to be constructed on 



