334 Professor Forbes's Fourteenth Letter on Glaciers. 



Daily motion in inches. 



Glacier des Bois, No. II., minimum in January, 

 Glacier des Bois, No. II., maximum in July, . 



Ratio of maximum to minimum, . 

 Glacier des Bossons, No. I., minimum in March, 

 Glacier des Bossons, No. I., maximum in May, 



Ratio of maximum to minimum, . 

 Glacier des Bossons, No. II., minimum in March, 

 Glacier des Bossons, No. II., maximum in June, 



Ratio of maximum to minimum, . 



2.Q 

 14-6 



5^:1 

 12-9 

 42-9 



"siTi 



10.2 

 32-3 



3^:1 



From these observations we may deduce the annual motion from 

 November 1844 to November 1845 with considerable exactness. 

 Allowing for the fractional parts of a year, we obtain the following 

 results, amongst which I have included a separate computation of 

 the mean daily motion for the summer period (April — October), and 

 the winter period (October — April). 



Table II. 



Motion for 365 days, November 

 1844 to November 1845, . . 



Mean daily motion, 



Mean daOy motion, summer period, 



April to October, 



Mean daily motion, winter period, 



October to April, 



Ratio, summer : winter, motion. 



Bois, 

 No. I. 



Feet. 



847-5 

 Inches. 



27-8 



37-7 



19-1 

 2-0:1 



Bois, 

 No. II. 



Feet. 



220-8 

 Inches. 



7-3 



9-9 



4-7 

 2-1 :1 



No. I. 



Feet. 



657*8 



Inches. 



21-6 



28-0 



15-8 

 1-8:1 



Bossons, 

 No. II. 



Feet. 



489-1 



Inches. 

 161 



22-2 



10-7 

 2-1:1 



I. From this Table we deduce in the first place a mean annual 

 motion far greater than has hitherto been observed, or perhaps sus- 

 pected in any glacier, that of near 300 yards, or almost one-sixth of 

 a mile. This is on the Glacier des Bois beneath the Chapeau, where 

 the inclination of the glacier is very steep, adding a new illustration 

 of the general principle,* that in similar circumstances the velocity 

 increases with the slope. To this cause may be added the high 



* Travels, 2d Edit,, p. 371. 



