HINTS TO TRAVELLERS. 
80 
out new rock-basins, or only cleaned out, scratched, and preserved from 
filling-up by alluvial deposits or earthslips, existing basins ? What is the 
general character of the valley bottom and slopes above and below the 
most conspicuous ancient moraines ? 
The depth of mountain lakes and the position of the point of greatest 
depth should be ascertained wherever possible. The marginal rock 
structure of lake basins, particularly near their outlet, is of some im¬ 
portance with a view to ascertaining whether they are true rock basins, 
or whether they are reservoirs formed by ancient moraines, earthslips, or 
alluvial deposits. 
The traveller or surveyor should, if possible, paint a mark and date on 
any conspicuous rock in situ parallel with the termination of the glacier 
at the time of his visit, marking the distance in yards of the ice from it. 
The next visitor will then be able to measure the movement that has 
taken place since his predecessor’s visit. Leaving out of question elabo¬ 
rate trigonometrical methods, such, for instance, as have been carried 
out on the Rhone Glacier in Switzerland, the following plan gives very 
valuable results, and demands no other instruments than a small jar of 
paint, a brush, a measuring tape, and a pocket compass. To ascertain 
the recent retreat of a glacier, measure the distance from the end of the 
ice in front of the longitudinal axis of the glacier to the most advanced 
terminal moraine, where vegetation first shows itself. The bare ground 
recently left by glaciers is easily recognisable. The diminution of volume 
is best measured by ascertaining the height of bare soil left on the sides 
of the lateral moraines in the portion of the glacier within the zone of 
vegetation. All photographic representations of the glacier end, and of 
the ground which has been freed from the glacier ice, are of great value. 
Those will be of most service that show the position of the glacier-snout 
with relation to some conspicuous rock or other feature in the local 
scenery. Each photograph should be dated, and the bearings and 
distance of the camera with reference to any such feature accurately 
noted. 
It is very important to investigate the state of various glaciers as regards 
advance or retreat. Neighbouring glaciers often furnish very different 
results in this respect, owing to the fact that steep glaciers anticipate in 
their oscillations those the beds of which are less inclined. To ascertain the 
oscillations of glaciers, it is necessary to fix the actual position of the ice* 
