250 Dr. A. P. Young—Glaciation of Navis Valley. 
The question whether the last stand at 2650 metres was an event 
in the closing history of the Ice Age as the Daun advance, or merely 
a recent incident of climatic oscillation, is left undecided. 
The level of the snow-line when it stood for a second time over the 
Griibl may have been somewhat lower than the first stand near 
2400 metres ; so also the second stand in the Upper Tarntal may have 
been somewhat under 2650 metres, the new floor in both cases being 
lower than the old. 
Tue Navis Vattry Drirr. 
The assumption underlying all the above conclusions, namely that 
snow-line and firn-line coincide, is safe enough as regards the small 
glaciers of the corries, and is probably not far from the truth in the 
ease of the glaciers taking their rise in the Tarntal Mountain, 
especially during the retreating stages, when the area covered by 
firn and snow was never very large. It may, indeed, be doubted 
whether at so high a level as that of Navis (1343 metres) any glacier- 
ice was contributed by the firn from the Tarntal during the extreme 
of the Wiirm period, when the snow-line was below 1200 metres at 
the northern border of the Alps. 
On the evidence of erratics from the Central Alps, it has been 
inferred that the ice-surface in the Inn Valley during the last 
maximum of cold must have reached a height of 1800 metres or 
more.’ The snow-line in these parts could not at the time have 
been higher than 1200 metres. The significance of the evidence will 
be considered later. It seems that under circumstances massive ice 
may accumulate much above the level of the snow-line at the place. 
The Inn Valley glacier in this case must have formed a high dam 
in front of its tributary the Sill.* It does not follow from this that 
the ice in the Sill Valley rose to the same high level. The ice 
flowing from the Inn up the Sill Valley was retarded by friction and 
wasted by ablation. It met the Sill glacier at the point at which the 
two tongues had equal amounts of moving energy. The Navis Valley 
in turn was dammed by the ice of the Sill, and it is important to 
determine the height of the ice-surface in this valley during the 
Wiirm period. 
At a level of 13800 metres, close to the settlement of Navis, are 
found some blocks of gneiss which could only have been brought by 
the ice of the Sill Valley (or Wipptal) to which the Navis is tributary. 
The blocks probably came from the Olperer Alps. They were borne 
down the Sill tributary in the Valsertal, and were carried by the back 
flow of the Sill ice into their present position. 
I learn from the Pfarrer of Navis, who first called my attention to 
these blocks, that the stone is in good demand for building purposes, 
and that one big boulder of gneiss has been quarried completely away. 
I take this opportunity of expressing my thanks to the Pfarrer, the 
Rev. Johann Schileo, for this and for much welcome information 
concerning the topography, many useful names being incorrectly given 
or omitted altogether on the maps. 
1 A. Penck & E. Briickner, Die Alpen vm Liszeitalter, 1907-9, pp. 268, 1148. 
* See Map, p. 341 of this Magazine for August, 1909. The Sill is the stream 
shown on the western border of the map, reproduced here on p. 246. 
