10 Canon Bonnet/ — 3foraines and Mud-streams in the Alps. 



size, some being nearly a hundred cubic yards in volume. This, 

 which descended in August, 1835,^ after unusually heavy rains, 

 appears to have been started by the fall of a large mass from the 

 crags of the Dent du Midi, which was augmented on its course by 

 snow and rock debris, and rendered more liquid by swollen torrents, 

 till it descended to the Rhone like a stream of lava. These instances 

 may suffice, though it would be easy to add to their number.'^ 



Mud avalanches and fans of debris are on a grander scale in 

 the mountains of Hindustan. Sir Martin Conway mentions them 

 in his well-known book "Climbing in the Himalayas." For 

 instance (p. 127), the valley of the Indus near Bunji is broad and 

 flat-bottomed; on the western side "is a mighty wall of rock, on 

 the eastern it is bordered by steep slopes." The slopes and the 

 wall, he thinks, cannot meet at a less depth than 500 feet below 

 the bed of the valley, and not improbably at one much greater. 

 " By what processes were these vast debris accumulations brought 

 together ? The problem is of general interest, for the Bunji valley 

 may be regarded as typical of Central Asian valleys generally, and 

 what is true of it is true also of the Pamir valleys and of those in the 

 regions of Western Tibet and Eastern Turkestan. .... It is 

 clear that the valleys have not been filled by the agency of bursting 

 lakes. The gentle dip of the bedding of the debris towards the 



river proves that the stuff came from the side slopes 



The question arises. How was such a quantity formed and caused 

 to descend ? Here the reader must bear in mind the nature of the 

 climate in the regions under consideration ; it possesses two main 

 qualities, extraordinary dryness and extreme and rapid variation of 

 temperature. The rainfall is trifling over the whole area, except 

 where the mountains reach great altitudes, and there snow is pre- 

 cipitated in considerable quantity. .... Throughout all the 

 region there is constantly being provided a mass of loosened debris 

 such as is never found in the better known mountains of Europe." 

 The low slope of this valley deposit, sometimes barely 3°, and the 

 large area covered, he goes on to say, prevent us from referring it 

 to ordinary bergfall, and makes ' mud avalanches ' the only possible 

 explanation. These have been seen actually descending by various 

 travellers — Colonel Godwin- Austen, Sir William Lockhart, Dr. and 

 Mrs. Bullock Workman ; indeed, the last named had a rather narrow 

 escape from one.' Sir Martin Conway himself saw two come down 

 a gully near the Hispar glacier, one just before, the other just after 

 his party crossed it.^ "It was a horrid sight. The weight of the 

 mud rolled masses of rock down the gully, turning them over and 

 over like so many pebbles, and they dammed back the muddy 

 torrent and kept it moving slowly but with accumulating volume. 

 Each of the big rocks that formed the vanguard of this avalanche 



1 A summary of the facts will be found in Joanne, " Itineraire de la Suisse," 

 Eoute 25 (between St. Maurice and E'vionnaz) . 



2 See also Dr. A. Irving, Quart. Journ. Geol. Soc, vol. xliv (1888), p. 158. 

 2 "In the Ice World of Himalaya," p. 156. 



* " Climbing in the Himalayas," p. 323. 



