no Mr. H. H. Howorth on 



In 1845, ^^ made some detailed experiments upon the 

 respective motion of glaciers at their surface and base. He 

 made elaborate measurements on the terminal face of the 

 Glacier des Bois at points 8, 54, and 143 feet respectively,, 

 above the bed or floor of the glacier. The result confirmed 

 his anticipations, that the effect of friction in retarding 

 motion is most sensible the nearer one gets to the base. The 

 measured motion of the three points was as follows : — 



Feet. Feet. Feet. 



2*87 4*i8 4-66 



being after the ratio of I 'oo 246 and 1*62. 



These results were confirmed by measurements made by 

 MM. Dollfuss and Martins, and published in the Comptes- 

 Rendus of the Academy, for October 26th, 1846. Their 

 measurements were made on the lateral face of the glacier,, 

 and the two sets of measurements combined exactly with 

 the demand made by Mr. Hopkins in the paper already 

 cited. Forbes also shewed, by careful measurements with the 

 theodolite, that the motion of a glacier is perfectly regular 

 and continuous from point to point, and leaves no room for 

 jerks and jumps, such as Hopkins had postulated. 



Forbes's experiments may be supplemented by an easy 

 appeal to another kind of evidence. As Dr. M. Williams 

 says : " Crevasses of considerable magnitude are commonly 

 formed without severing one part of a glacier from another. 

 They are usually V-shaped in vertical section, and in many 

 the rupture does not reach the bottom of the glacier. Very 

 rarely indeed does a crevasse cross the whole breadth of a 

 glacier in such a manner as to completely separate, even 

 temporarily, the- lower from the upper part of the glacier " 

 {Quarterly Journal Sc, Vll. 221). This shews that the 

 upper part of the mass of ice has a greater tension, and 

 moves faster where the tension is removed than the lower. 

 In fact, a glacier is literally a frozen river, and just as the 

 water near the banks of a river is dragged and stopped by^ 



