28 MAN AND THE GLACIAL PERIOD. 



of the Muir Glacier. I measured one block of stone 

 which was twenty feet square and about the same height, 

 standing on a pedestal of ice three or four feet high. 



The mountains forming the periphery of this amphi- 

 theatre rise to a height of several thousand feet ; Mount 

 Fairweather, upon the northwest, from whose flanks prob- 

 ably a portion of the ice comes, being, in fact, more than 

 fifteen thousand feet high. The mouth of the amphi- 

 theatre is three miles wide, in a line extending from 

 shoulder to shoulder of the low mountains which guard 

 it. The actual water-front where the ice meets tide-water 

 is one mile and a half.* Here the depth of the inlet is 

 so great that the front of the ice breaks off in icebergs of 

 large size, which float away to be dissolved at their leisure. 

 At the water's edge the ice presents a perpendicular front 

 of from two hundred and fifty to four hundred feet in 

 height, and the depth of the water in the middle of the 

 inlet immediately in front of the ice is upwards of seven 

 hundred feet; thus giving a total height to the precipitous 

 front of a thousand feet. 



The formation of icebergs can here be studied to 

 admirable advantage. During the month in which we 

 encamped in the vicinity the process was going on con- 

 tinuously. There was scarcely an interval of fifteen 

 minutes during the whole time in which the air was not 

 rent with the significant boom connected with the " calv- 

 ing " of a berg. Sometimes this was occasioned by the 

 separation of a comparatively small mass of ice from near 

 the top of the precipitous wall, which would fall into the 

 water below with a loud splash. At other times I have 

 seen a column of ice from top to bottom of the precipice 

 split off and fall over into the water, giving rise to great 

 waves, which would lash the shore with foam two miles 

 below. 



* These are the measurements of Professor Reid. In my former 

 volume I have given the dimensions as somewhat smaller. 



