1899.] NATURAL SCIENCES OF PHILADELPHIA. 505 



ILLECELLEWAET GLACIER. 



Owing to its accessibility, this glacier has been more carefully 

 observed than any other in the region. It may^be reached by a 

 good trail in thirty niiuutes from Glacier House, and we visited it 

 almost daily between the 29th of July and the 20th of August of 

 the present year. During this period, partly owing to the cold 

 and damp weather, but little melting or recession of the tongue 

 was noted. This was in marked contrast to the rate of melting 

 observed last year.' 



The observations on this glacier naturally divide themselves 

 uader four principal heads, which will be taken up as follows: 



1. Measurements of rate of flow. 



2. Measurement of recession and other changes since 1898, 



3. Photographic record from test rock " "W." 



4. Survey of tongue, and mapping moraines and streams. 



1. Measurements of rate of flow. 



These were determined at nine points on the glacier, one a few 

 feet above the tongue, and eight on a straight line at right angles 

 to the flow and about 1600 feet above the tongue. Rev. Wm. 

 S. Green, in 1888,'' made a determination of the rate of flow by 

 driving stakes into the ice in a direct line. Owing to the rapid 

 melting, however, these soon fell, and when he returned to 

 remeasure, no accurate results could be obtained. Profiting by 

 his experience, we decided to employ plates of steel, six inches 

 square and one-eighth inch thick, in the centres of which holes 

 were bored and threaded to receive three-quarter-inch pipes, three 

 inches long. The original purpose of the pijDCS was to support 

 small flags to facilitate observation. It was found, however, A^hen 

 the practical test came to be made, that if the plates were inverted, 

 with the pipes extending on the under side, they sank into the ice, 

 forming anchors, while the plates rested on the surface and could 

 be easily seen. The plates were given two coats of vermilion 

 paint, and lettered and numbered in white for identification. 



The right moraine of the glacier being high and secure, and 



« Proc. Acad. Nat. Sci. Phila., 1899, p. 123. 

 * Among the Selkirk Glaciers, p. 218. 



