XX Annual Address. | February, 1918, 
Although there is some doubt as to the underground form of 
the trough below the main mass of alluvium, there is none as to 
its relationship to the Himalaya, for its boundary is open to ae- 
tual observation and is known to be the zone of fracture already 
referred to as the main boundary fault. Not one, but many 
faults parallel to the mountain foot have been traced; they 
stand as records of fractures that have occurred in the crust in 
comparatively recent geological times, and indicate planes of 
weakness along which movement may again take place. 
Assam faults of the Shillong earthquake of 1897 bear witness 
that such movement still takes place from time to time. r- 
ther evidence of movement along the main boundary fault is 
also found in changes of relative level that took place in 1906, 
at the time of the Kangra earthquake, between Mussoorie and 
Dehra Dun. 
Faults or fractures along and near the Himalayan moun- 
tain foot must, therefore. be regarded not only as planes on 
planes on or near which it may occur in the future. The ef 
they were no doubt the loci of violent earthquakes, that te 
a 
of comparative stability and quiescence, whereas the crust aa 
the foot of the Himalaya is in a state of strain, being the 
affected. by those mountain-building forces which, during 
last geological period, produced the Himalayan system. 
. . d we ‘ 
pur and Arrakan on the east, that we should expect Tr we 
deal with 
made 
