72 THE ICE AGE IN NORTH AMERICA. 



parative narrowness of the area of most rapid motion, the 

 average movement of the mass is probably not over twenty 

 feet per day, and this amount would perhaps account for 

 the number of bergs floating away with the tide, especially 

 since now we must add to them the amount supplied by the 

 recession of the front of the ice. 



With reference to the evidence of the recent recession of 

 the glacier Professor Reid agrees entirely with me. By com- 

 parison of his photographs with mine he found that in "the 

 four years from 1886 to 1890 the western end of the ice front 

 has receded 1,200 yards and the eastern end 750 yards. The 

 center also has receded about 1,000 yards, so that the average 

 recession of the ice front is a little over 1,000 yards in the 

 four years, or, say a mile in seven years .... It does not 

 seem at all incredible that the ice from the various glaciers of 

 Glacier Bay may have united to fill a large part of the bay 

 100 years ago." 



But it is no longer necessary to depend on this evidence 

 alone. In 1906 Messrs. F. E. and C. W. Wright made an 

 official investigation of the region with the following startling 

 results. On comparing their map with that of Professor Reid 

 made in 1892 they write that: 



Beginning with Muir Glacier and its tributaries the ice 

 front has receded a maximum distance of 33,000 feet; Dirt 

 Glacier is no longer tidal; White and Adams Glaciers are 

 supplying very little ice to the general ice field; Morse Glacier 

 terminus is about one mile from tide water .... Girdled 

 Glacier and Berg Lake have not changed materially in aspect. 

 The length of the total ice front of Muir Glacier is now over 

 40,000 feet instead of 9,000 feet in 1892. The present ice 

 front passes at its northern extremity at about the position 

 of your 1,000 foot contour on the ice of 1892. This remarkable 

 decrease in elevation is undoubtedly due not only to melting 

 down but also to breaking down of the exposed ice masses. 

 The ascent of the ice mass at this point is decidedly steep and 

 the ice fairly cascades into the water. The present height of 

 the ice fronts of all the tide water glaciers is about the same 



