694 
PROFESSOR PRESTWICH OR THE ORIGIN 
larger lakes which end by bursting and sweeping away their barriers, when they 
produce the most devastating effects, as in the instances of the Skarclo and the Drance 
inundations; of the third class we know little, as they are rare, and the scale on which 
they occur in Europe is comparatively insignificant. In hot seasons there may be here 
ancb there a few temporary ponds formed on the ice, but as a rule it is only in countries 
in which the glaciers descend into valleys where the summer heat is considerable, that 
we find these large glacier lakes of this description. 
In the Alps this latter class of lakes is met with on a few of the glaciers in the 
form of pools, generally small (baignoires, of Agassiz) ; still some of these attain the size 
of from 20 X 20 metres to 20 X 40 metres. They move with the glacier, and drain 
sometimes suddenly through fissures while at other times they last for years. A remark¬ 
able one attaining the dimensions of a small lake has been described by Dolfuss- 
AussetA It was noticed in 1842 on the Aar glacier near the confluence of the 
Thierberg glacier. It then had a superficies of 10 acres with a depth of 206 feet, and 
was surrounded by steep cliffs of ice over which glacier detritus was constantly tumbling 
and gradually filling up the lake. As showing how compact some glacier ice may be, 
this small lake lasted 24 years, and was carried a distance of 600 feet at a rate of about 
25 feet annually. 
In the Himalayas, lakes of this class are not uncommon. Sir Joseph Hooker notices 
one part of the Kinchinjhow glacier, where it was half a mile wide and the surface 
very undulating (“like a troubled ocean”), which he found covered with large pools of 
water, one of which was 90 feet deep.t 
But it is in the part known as the Mustakh range that these lakes are most numerous. 
In Colonel Godwin-Austen’s account of that range many such bodies of water are 
described. On the Purnnah glacier,| where the surface is either a succession of ridges 
more or less stony, or where in other places it resembles “ a sea of frozen waves,” “ small 
pools of emerald-green water ” fill many of the hollows and are surrounded with cliffs 
of ice ; in some parts there are streams of running water which often end abruptly by 
discharging down some crevasse. On the Baliio glacier there are hollows filled with 
water forming lakes often as clear as crystal, and of great depth. Some of these lakes 
measured as much as 500 yards in length and from 200 to 300 yards in breadth, and 
were spread over a distance of more than 2 miles along the centre of the glacier which 
was there very level. § 
First, deep hollows and then lakes are formed by the damming back of the glacier 
streams. The barriers between the lakes are constantly giving way, so that the lakes 
* Op. cit., yoI. v., p. 460. 
f ‘ Himalayan Journals,’ vol. it, p. 134, 1854. 
% Jonrn. Roy. Geogr. Soc., vol. 34, p. 31. 
§ Ibid. p. 38. Colonel Godwin-Austen informs me that on the lower part of tlie Baltero glacier, the 
long parallel moraines get arrested in their course, and run one into the other, and thus form stony 
barriers. 
