96 THE EOEMS OF WATER IN 



242. The ice-stream here referred to is the Morter- 

 atsch glacier, the end of which is a short hour's walk 

 from the village of Pontresina. We have now to de- 

 termine its rate of motion and to account for the widen- 

 ing of its medial moraine. 



243. In the summer of 1864 Mr. Hirst and myself 

 set out three lines of stakes across the glacier. The 

 first line crossed the ice high up ; the second a good 

 distance lower down, and the third lower still. Even 

 the third line, however, was at a considerable distance 

 above the actual snout of the glacier. The daily 

 motion of these three lines was as follows : — 









First Line. 













Stake . 



. 1 



2 



3 4 5 6 



7 



8 



9 



10 



11 



Inches . 



. 8 



12 



13 13 14 13 

 Second Line. 



12 



12 



10 



7 



5 



Stake • 



. 1 



2 



3 4 5 6 



7 



8 



9 



10 



11 



Inches . 



. 1 



4 



6 8 10 11 

 Third Line. 



11 



11 



11 



11 



11 



Stake . 



. 1 



2 



3 4 5 6 



7 



8 



9 



10 



11 



Inches . 



. 1 



2 



4 5 6 6 



7 



7 



5 



5 



4 



244. Compare these lines together. You notice the 

 velocity of the first is greater than that of the second, 

 and the velocity of the second greater than that of the 

 third. 



245. The lines were permitted to move downwards foi 



