1845.] MOTION OF GLACIERS OF THE SECOND ORDER. 75 



position, their great absolute height, and their usually very 

 steep declivity and small surface, give considerable interest to 

 the determination of their rate of motion, at least approximately. 

 Accordingly, I seized the occasion of spending some days in 

 July 1844, at the Hospice of the Simplon (already at a height 

 of 6600 feet above the sea), to examine and measure the pro- 

 gress of the small glacier which hangs from the slope of the 

 Schonhorn, immediately behind it, and 1400 feet higher. I 

 intend to give elsewhere a minute account of this glacier, and 

 my observations upon it ; but in the mean time I may state that 

 one of the marks observed, at a point having an inclination of 

 10, moved at the rate of 1.4 inches in 24 hours ; and another, 

 at an inclination of 20, moved 1.8 inches in the same time. 

 This small result is quite conformable with the dry and powdery 

 condition of such elevated glaciers, yielding little water, and 

 capable of exerting, on their under parts, a very trifling hydro- 

 static pressure.* 



Exactly analogous results were obtained by M. Agassiz's 

 coadjutors at a somewhat later period of the same year. The 

 experiments are fully detailed in the Comptes Rendus ; f and 

 the conclusions which are deducible from them, are (1.) That 

 the daily motions of these small glaciers, which rested on beds 

 so highly inclined as from 15 up to 33, are included between 

 20 and 72 millimetres (0.79 to 2.84 English inches) per diem. 

 (2.) The observers think that their observations go to prove 

 that when these glaciers are prolonged far enough to meet the 

 main glacier below, and to unite their streams, then the lower 

 part of the tributary glacier, or that nearest the point of union, 

 moves SLOWER than the upper part, or that nearest the origin 

 of the little glacier; but, on the contrary, if the glacier be 

 pendant on the slope, and the lower end decays away without 

 joining the principal, then the inferior extremity moves FASTER 

 than the origin. Now the cause of this variation in the two 



* This experiment is briefly mentioned at the close of my Eighth Letter on 

 Glaciers. 



f P. 1303, and two following pages. 



