1082 The American Naturalist. [December, 
General Notes. 
GEOLOGY AND PALEONTOLOGY. 
Mud Avalanches in the Mustagh Mountains.—During a 
recent exploration in the Mustagh Mountains in India, Mr. W. M. 
Conway noticed the accumulation in the valleys, of debris consisting of 
stones as often rounded as angular, embedded in mud. In the Gilgit 
valley this accumulation reaches a depth of 1000 feet or more. The 
author claims that the work of filling up the valleys, not only in the 
Mustagh Mountains but all the deeply filled valleys characteristic of 
the Central Asian plateau, has been done by mud avalanches, and he 
gives the following interesting account of one of which he was an eye 
witness. 
“ We were just approaching the mouth of a deep, narrow nala that 
crossed our path when we heard a noise as of continuous thunder, and 
beheld a vast black wave advancing down it at a rapid pace. Some 
accumulation of water had got loose high aloft, and the flood was bring- 
ing the hill down with it. When we reached the edge of the nala the 
main mass of the stuff had gone by and only a thick, black stream of 
mud was rushing swiftly past. This became by degrees more liquid 
until it was no longer mud but black water. We waited for some time 
till the waters subsided. At length Harkbir found a way across the 
torrent by leaping from stone to stone. We had begun to follow him 
when Karbir, who was looking up the nala, shouted to us to come 
back, which we did with the nimblest feet. We were not more than 
out of the ditch before another huge mud avalanche came sweeping 
down. It was a horrid sight. The weight of the mud carried huge 
masses of rock down the gully, rolling them over and over like so many 
pebbles, and they in turn dammed back the muddy torrent and kept 
it moving slowly with accumulating volume. Each of the big rocks 
that formed the vanguard of this avalanche weighed many tons; the 
largest were about 10 feet cubes. The stuff that followed them filled 
the nala to a width of about 40 feet and a depth of about 15 feet. The 
thing moved down at about the rate of five miles an hour. When the 
front of the avalanche was gone, and the mass of stuff became shallower, 
the mixture was about half mud, half rocks, and flowed faster. Now. 
and again a bigger rock than the average would bar the way ; the mud 
