632 REPORT—1904. 
journey continued along the north-eastern shore of the lake, with digressions into 
the eastern mountains, and plants were collected up to about 16,500 feet. The 
majority of the plants show a striking uniformity as regards their vegetative habit, 
and grow usually in rosettes or mounds; they have long tap roots, which enable 
them to absorb water from the warmer soil at a considerable distance below the 
surface, and their leaves are usually linear and often hairy. ‘These peculiarities 
are induced by the climatic conditions, since the plants have to endure a burning 
sun during the day, followed by frost, with cold, cutting winds, at night; there is 
often a difference in temperature of as much as 70°F. in a few hours, The 
journey was continued round the northern end of the lake, where the Indian 
huts are built of mud bricks in the shape of beehives, and was terminated at the 
Peruvian port of Puno, whence runs the railway to Arequipa and Mollendo, 
2. Glacier-bursts. By Cuartes Rasor. 
Glaciers give rise to torrential phenomena known by the name of ‘ débacles,’ or 
glacier-bursts, the geological importance of which has hitherto been insufficiently 
recognised. 
The production of an outburst depends on the prior creation of a reservoir of 
water and its sudden discharge. The creation of this reservoir may be the result 
of an advance or retreat of the glacier, which has the effect of stopping the out- 
flow of the waters into a thalweg ; it may equally be the consequence of the 
present state of the glaciation, which may permanently block the valley. Lastly, 
the body of water necessary to the production of an outburst may be formed 
either above or below the glacier, or even within its thickness. When the barrier 
of ice yields the outburst takes place, and its violence is proportional to the cubic 
contents of the reservoir and the slope of the ground over which the inundation 
passes. In the Alps twenty-five glaciers have been the scene of outbursts, either 
singly or in series, whose causes are matter of knowledge, but many others 
have produced inundations whose mode of origin has escaped observation. The 
total number is certainly much greater, but only the most destructive had been 
recorded prior to 1892, the date of the Saint Gervais catastrophe. 
These torrential phenomena occur in all the glaciated mountain regions of the 
world—in Norway, Iceland, Spitzbergen (where Sir Martin Conway and Professor 
KE, J. Garwood have noted their effects), in Greenland, Alaska, and, lastly, in the 
Himalayas. In the last-named region English travellers, like Col. Godwin-Austen, 
Sir Martin Conway, and Professor Norman Collie, have collected valuable data 
bearing on this phenomenon. In the Alps, the volume of water precipitated in 
the case of destructive outbursts may reach several million cubic métres, and this 
enormous liquid mass may flow away in a few hours over steeply sloping ground. 
In 1878 the Marjelensee discharged 7,700,000 cubic métres in nine hours, and the 
Gietroz outburst in 1818 attained a volume of 530 million cubic feet. 
Such a mass of water moving at an enormous speed has an important erosive 
effect, and modifies the contours of the valley along which it takes its course. On 
the other hand, it carries with it enormous masses of material, and, frequently, 
large numbers of trees, All these débris are afterwards deposited in the locality 
where a diminution of the angle of slope brings about a reduction in the rate of 
flow. Thus, in valleys visited by frequent catastrophes, we may say that the 
glacial deposits of the present day or of Pleistocene age have been, and are still 
being, shifted and rearranged throughout the whole of the zone affected by these 
wild waters. Similar inundations must necessarily have been very frequent 
during the glacial epoch, and frequent mistakes must have been made in studying 
the Pleistocene formations through not taking account of these phenomena. 
Still, we must not go too far and exaggerate the action of glacier-outbursts, Their 
effects are at the present day limited to the sides of the thalwegs, and the same 
must have been the case during the Quaternary period. 
