22 ALASKA GLACIERS 



by Reid. The accompanying map (fig. 10) is copied from 

 Reid, with the addition of Gannett's line showing the con- 

 dition on June 10-12, I899- 1 



From 1880 to 1886 the cliff retreated about 4,000 feet; 

 from 1886 to 1890, 3,300 feet. Between 1890 and 1892 

 there was an advance of 700 feet; between 1892 and 1899 

 a retreat of about 1,900 feet, nearly the whole of the 

 change occurring after 1894. The net retreat in nineteen 

 years was 8,500 feet, or 1.6 miles. 



Although several of these surveys were quite accurate, 

 I have stated their results in round numbers, because 

 greater refinement would tend to mislead. The forward 

 flow of the glacier probably varies little from day to day, 

 but the breaking away of the cliff is quite irregular and 

 the outline of the front continually changes. Besides this 

 change in local detail there is a general change of more 

 permanent character, to be described presently; and it is 

 probable that an important seasonal oscillation interferes 

 with the direct comparison of observations made at differ- 

 ent times of year. The average annual retreat of the ice 

 cliff for the four years preceding 1890 was 800 feet, and 

 for the following two years the average advance was 350 

 feet; but Reid noted in the summer of 1890 a retreat of 

 500 feet in 43 days (July 26-September 7), equivalent 

 to an annual rate of 4,000 feet. Again in 1892 he made 

 two observations 31 days apart (July 19- August 19), 

 and these show retreat at the rate of about 3,500 feet per 

 annum; but the whole retreat in the seven following years 



1 Reid's map is pi. xcva in i6th Ann. Rept., U. S. Geol. Surv., part i, 1892. 

 Gannett's work was limited to the changed ice front and the resulting extension 

 of the shore line. Field notes and photographs show that there were associated 

 changes in the drainage of the gravel plains, but as these data are not sufficient 

 for the correct delineation of the streams in 1899 I have left them as Reid repre- 

 sented them. Some time before 1894 the northern branch of the western creek 

 found a shorter course to the inlet, reaching tide about three-fourths of a mile 

 nearer the glacier ; and some time between 1894 and 1899 a similar change oc- 

 curred on the east side of the inlet. 



