Yol. 51.] MR. J . E. MARK ON THE TARNS OP LAKELAND. 35 



4. The Tarns of Lakeland. By J. E. Mare, Esq., M.A., F.B.S., 

 Sec.G.S. (Bead December 5th, 1894.) 



Contents. 



Page 



I. Introduction 35 



II. Tarns near Ha wes water 37 



III. Tarns between the Grasmere and Langdale Valleys 38 



IV. Coniston Tarns 40 



V. Tarns between the Duddon Valley and Wastdale 42 



VI. Tarns in the Scawfell Group 43 



VII. Tarns between Borrowdale and Thirlinere 45 



VIII. Conclusions 46 



I. Introduction. 



When discussing the origin of lake-basins, and maintaining the 

 possibility of some of our English lakes lying in basins formed by 

 oarth-movement, I have often been asked whether I should consider 

 that the basins of mountain-tarns could have been formed in that 

 way. The difficulty of their being so formed seemed very great, 

 and, supposing that they were true rock-bound basins, the conclusion 

 appeared unavoidable that they were eroded by the action of ice. 

 Some time ago I saw reasons for believing that certain tarns of 

 "Westmorland, though apparently in rock-basins, were not really 

 so, and accordingly I have devoted some time during this year to 

 the examination of a number of the tarns of Cumberland, West- 

 morland, and the Furness district of Lancashire, and now offer my 

 observations to the Society as a contribution to the study of the 

 origin of lake-basins, without in any way attempting to open up 

 the question as to the origin of our larger lakes. 



A casual glance at many of these tarns shows that the stream 

 which issues from them runs over solid rock close to the surface of 

 the lake, and this appears to have been considered by some a 

 satisfactory proof that the tarn itself occurs in a true rock-basin. 

 It is the object of this paper to show that such is not the case. All 

 who have written upon the tarns of the district agree that there 

 are some which are partially or wholly moraine-dammed at the 

 exit (using the term ' moraine-dammed ' to include such as are 

 stopped by talus sliding down snow-slopes, as suggested by Clifton 

 Ward in the case of Bowscale Tarn). Such moraine-dammed 

 tarns will necessarily have a comparatively brief existence, should 

 the exit of the lake immediately overlie the old river-bed, for the 

 morainic material will be easily denuded. Accordingly we find 

 numbers of instances of old tarns now converted into peat-bogs, 

 owing to the temporary barrier of drift having been denuded. But 

 there must have been many cases where the lowest point of the 

 morainic barrier did not lie vertically above the bottom of the old 

 moraine-filled valley. In such cases the stream would cut down 



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