1899.] 



NATURAL SCIENCES OF PHILADELPHIA. 



507 



Table showing Motion of Line of Plates, across Illecelleicaet Glacier, 

 British Columbia, July Slst to September 5th, 1899. 



Again, on September 5, through the kindness of Mr. E. J. 

 Duchesnay, of Revelstoke, B. C, another measurement was made 

 by Messrs. H, B. Muckleston and C. E. Cartwright. The posi- 

 tions of the plates on July 31st and September 5th only are shown 

 on the map, as the motion which had taken place up to August 

 11th was so small as to be hardly noticeable on that scale. 



These determinations show a marked decrease in the rate of flow 

 as compared with the observations of Rev. William S. Green in 

 1888. They demonstrate the more rapid motion of the central 

 portion of the glacier, and also that the ice on the convex side of 

 the line of flow moves faster than on the concave side. 



Two of the plates, Nos. 4 and 8, could not be found on Septem- 

 ber 5th. All the plates were left on the ice, and it will be interest- 

 ing to determine the amount of flow during an entire year if they 

 can be found again next summer. 



Besides the row of eight plates across the glacier, an addi- 

 tional plate (No. 9) was placed a few feet above the tongue and 

 measured at frequent intervals. The slope of the ice at this point 



