GLACIAL PERIOD. 
13 
mann’s work upon the Alps. In 1740, Ka- 
peler, a physician of Lucerne, undertook a 
journey to the mountains of the Aar, to visit 
certain crystal grottos, now well known, but 
then recently discovered. He prepared a map 
of these grottos and their vicinity,- in which 
they are represented as being situated at some 
distance from the extremity of the glacier, 
the lower end of which is now considerably 
beyond them.* 
But to return to the glacier of the Rhone. 
We can detect the sequence and relative age 
of its ancient moraines, not only by their posi¬ 
tion with reference to each other and to the 
present glacier, but also by their vegetation. 
The older ones have a mature vegetation; 
indeed, some of the largest trees of the valley 
stand upon the lower moraines, while those 
higher up, nearer the glacier, have only com¬ 
paratively small trees, and the more recent 
ones are almost bare of vegetation. More¬ 
over, we do not lose the track of the great 
* This map, with all its details and measurements, is re¬ 
produced (PI. V. fig. 1) in my “ Systeme Glaciare.” It was 
accompanied by an explanatory paper in the form of a letter 
to Altmann, then Professor at Berne. 
