346 Dr. A. P. Young— Structure of the Tarntal Mass. 



east side "by the Lizumbach. It had an exit on the north-west 

 corner over the Upper Tarntal, to which it was tributary (PI. XVIII, 

 Fig. 7). On the west side, nearer to the Reckner ridge, are seen 

 earlier and higher openings, by which it drained at one time directly 

 into the Griibl. 



All the exits of Upper and Lower Tarntal are now blocked by 

 accumulations of loose material, as seen in PL XVIII, Fig. 7. 

 These cannot be due simply to falls from the overlying slopes. The 

 debris must have been arranged by small ice-tongues which just filled 

 the valleys, and the dams represent true end-moraines. The snow- 

 limit at the time must have stood at 2650 metres nearly. 



The present snow-limit for the nearer high mountain-masses is 

 placed variously at 2700 to 2900 metres. 



Remembering that the snow-limit is higher the greater the mass of 

 the elevated portion of the crust, it would follow that the virtual 

 snow-line for the small mass of the Tarntaler Kopfe is now appreciably 

 lower than the summits (2830 to 2890 metres), but is ineffective in 

 the absence of level surfaces capable of retaining the snow. It is 

 probable that the high valleys have in recent times more than once 

 borne ice-tongues, and may again be filled on the occasion of a fall in 

 the mean annual temperature quite within the range of oscillation 

 possible under present conditions of climate. 



The Upper and Lower Tarntal contain several small lakes or ponds ; 

 there is one at the lower end of each valley just above the natural 

 dam. The water of these ponds often carries ice till midsummer, 

 another indication of their proximity to the present snow-line. 



In this paper the term snotv -limit has been used as equivalent to 

 the boundary between /?ni and glacier ice. This is perhaps not strictly 

 the case if we define the snow-line as the level above which a free 

 horizontal surface is covered the whole year round with snow. The 

 discrepancy does not affect the general line of reasoning. 



REFERENCES TO FIGURES OX PLATES XV-XVIII. 



Plate. Fig. 



XV. 1. The Tarntaler Kopfe from Mucheler Aim, 4 kilometres to "W. : fresh 

 autumn snow. Compare with Fig. 9 in text, p. 339. 

 2. The Tarntaler Kopfe; from the ridge of the Kreuzjochl, distant 

 3 kilometres to S.W. by W. Two summits, 2836 and' 2891 metres, 

 in the middle of the picture, belong to the main mass of serpentine 

 which shows dark against other rocks. 

 XYL 3. The ridge of the Nederer, showing the strong yertical jointing ; from 



s.s.w. 



4. Reckner (serpentine) on the right, Kahlewand (dolomite) on the left ; 



from the serpentine peak 2836 metres to W. of Reckner. 

 XYII. 5. The scree-cone (Issl) under the Lower Tarntal. From the lip of the 



Griibl corrie. 

 6. The head of the Lower Tarntal where the valley is beheaded by the 



Lizumbach ; looking eastward. 

 XVII L 7. Lake at the lower end of the Upper Tarntal, with moraine dam 



beyond ; looking westward. 

 8. The ridge to north of the Mieselkopf (2653 metres of map) ; looking 



westward. 



