542 



THE NATIONAL GEOGRAPHIC MAGAZINE 



t!?;l 



Photo by Lawrence Martin 



A SMALL PORTION OF THE FRONT OF MIFFS GLACIER, FROM TFIF BRIDGE ON COPPER 

 RIVER & NORTHWESTERN RAILWAY, COMPARED GRAPHICALLY WITH THE 

 HOTEL LA SALLE, IN CHICAGO, WHICH IS 3 10 FEFT HIGH 



Late in August, 1910, when the waves 

 were not as powerful as they had been 

 earlier in the summer, the largest ice fall, 

 or slough, from Childs Glacier which I 

 saw sent a wave across the river with 

 lightning rapidity, causing the water to 

 splash up over the 15 or 20 foot bank, 

 near where I stood, and back a short dis- 

 tance into the forest. It of course rose 

 highest directly opposite the ice fall, the 

 height of the wave on the bank decreas- 

 ing both up and down stream. Six or 

 seven ring-waves in succession splashed 

 far up the river bank, the first one visibly 

 running upstream against an eight or 

 nine mile an hour current. It was easy 



to see how the larger waves during the 

 first part of the summer were able to 

 cut back the river bank so easily. 



Near the north margin of the glacier 

 is an easily accessible portion of the ice 

 front which ends upon a nearly-flat out- 

 wash plain of glacial gravels, overgrown 

 with alder and cottonwood trees 50 to 

 100 years old. Here the glacier was 

 nearly without motion from 1905 to 

 1909, and probably for some years be- 

 fore, so that small shrubs had begun to 

 grow upon the stagnant ice margin. This 

 part of the glacier advanced 1,500 to 

 1,600 feet before June 10, 1910, and 204 

 feet more up to October 5. The rate of 



Dates of observations. 



Number 

 of 

 days. 



Advance 



, in feet. 



Rate per d 



ay, in feet. 



Fastest. 



Average. 



Fastest. 



Average. 



June 10 to July 29 



49 



124 



116 



2-5 



2.37 



July 29 to August 6 



8 



26 



2 3 



3.25 



2.87 



August 6 to August 11 



5 



4i 



8 



8.2 



1.60 



August 11 to August 17 



6 



27 



4 



4.5 



.66 



Aguust 17 to August 29 . 



12 



42 



19 



3-5 



1.58 



August 29 to September 19 



21 



37 



27 



1.76 



1.28 





17 



L3 





0.7 



• 44 



