Vol. 62.] ANNIVERSARY ADDRESS OF THE PRESIDENT. CXXV 



(2) The Glacial Period. 



I do not propose to treat of the glaciation of the district at 

 length. The writings of Clifton Ward in our own Journal and in 

 the Memoirs of the Geological Survey give an account of nearly 

 all that is known (mainly through his own labours) of the subject, 

 for little has since been done. 



We are at present concerned with the influence which the ice 

 exerted in the direction of modification of the drainage-lines. That 

 small diversions have been produced by ice is abundantly clear, the 

 examples already noted in the Langstrath valley being typical cases : 

 but it is doubtful how far diversion has occurred on a large scale, 

 owing to our ignorance of the events which happened during the 

 period of maximum glaciation. 



It is in connexion with the larger existing lakes that the evidence 

 seems most clear, as described in my paper on ' The Waterways of 

 Lakeland,' though all the cases therein noticed will not hold good, 

 as, for instance, that which I described in the case of Wastwater 

 along the line of Countess Beck. 



The presence of dry valleys at the foot of Bassenthwaite Water, 

 Thirlmere, and Windermere, however, points to diversion ; of these, 

 the most striking is that of Windermere, concerning which a few 

 remarks may here be made. 



In order to produce diversion, it is not necessary that a lake should 

 be formed entirely by the construction of a glacial dam. If the 

 lake is partly due to erosion or earth -movement, and partly to the 

 formation of a dam, the waters may be switched into another valley. 

 And here I must confess that, in papers which I have written in 

 former years, in discussing the origin of the lakes of this region, I 

 have overestimated the importance of these dams. As the result 

 of subsequent examination on. many occasions, I am convinced that 

 Watendlath Tarn and Elterwater among the smaller lakes, and 

 Thirlmere among the larger, lie in true rock-basins. This being so, 

 many of the other lakes may be partly in rock-basins, and owe not 

 their origin, but only an increase in size, to the barriers of Glacial 

 Drift. 



Windermere certainly owes its present water-level to such a barrier, 

 which, as I have elsewhere described, blocks the Cartmell Valley at 

 the foot of the lake. This valley is a wide important valley occupied 

 by an insignificant runnel. The water has been diverted into its 

 present course to the west of the old valley, passing Haverthwaite 

 and entering the Leven estuary. It is clear that this stream is 



