in the Summer of 1911. 



±75 



At the east ledge, on the contrary, detachment was gradual, 

 the dislocated masses of rock sliding downward with a long- 

 drawn roll of thunder, making it easy to know, when lying in 

 bed at the station, from which side of the pit an avalanche 

 5 shows the progressive demolition of 



was descending. 



Fig. 



Fig. 5. 



Fig. 5. Showing progressive subsidence and demolition of east black 

 ledge, August 1st and August 24th. 



the east ledge, and the reader should note in the lower view 

 that, not only the detached "block, but the entire ledge as well, 

 has settled to a lower level. 



Still more remarkable a phenomenon was the descent of the 

 ledge at the south side of the pit, where the entire mass of 



