x CONTENTS. 



Page 



'XIV. ELEVENTH LETTER ON GLACIERS. Addressed to PRO- 

 FESSOR JAMESON [1846] . . .169 



Observations on the Depression of the Glacier Surface... 

 Ablation and Subsidence distinguished and ascertained... 

 On the Relative Velocity of the Surface and Bottom of a 

 Glacier. 



XV. TWELFTH LETTER ON GLACIERS. Addressed to PRO- 



FESSOR JAMESON [1846] . . .176 



On the Extraordinary Increase of the Glacier of La Brenva 

 from 1842 to 1846... Its Motion in Winter, as observed 

 by M. Guicharda... Observations on the Veined Structure 

 in 1846, and Experimentum Crucis respecting its Origin, 

 with measurements of the motion of the Ice... Analogy 

 from the motion of the Rhone. 



XVI. THIRTEENTH LETTER ON GLACIERS. Addressed to PRO- 



FESSOR JAMESON [1846] ..... 187 



Acceleration of the Surface Motion of Glaciers confirmed... 

 Velocity of the Mer de Glace in the Summer of 1846 at 

 Stations C, D, P, and R... Velocity of the Glacier of 

 Talefre, near its point of Discharge . . .Discovery of a Knap- 

 sack ten years buried in the Ice, and deduction of the 

 motion. ..The Glacier of Nant Blancvisited, and its Motion 

 determined... The Glacier of Miage^re visited, and motion 

 measured... On the Conversion of the NeVe" into Ice... 

 Congelation of Infiltrated Water not necessary to produce 

 the Veined Structure... An attempt to explain the appa- 

 rent rejection of Stones from the Glacier... Ridges of Ice 

 in certain parts of Glaciers due to the bruising effect of 

 intense Pressure... Three Orders of discontinuity, Ridges, 

 Crevasses, Veined Structure. 



XVII. FOURTEENTH LETTER ON GLACIERS. Addressed to PRO- 

 FESSOR JAMESON [1847] . . . . 205 



On the Variation of the Motion at different Seasons... Obser- 

 vations on the Glacier of the Aar, considered and com- 

 pared with the Author's results. 



