NORWEGIAN GLACIERS. 75 



The next problem attracting attention was the determination 

 of the amount of mud in glacier rivers, in order to get some 

 well-founded idea as to the rate of erosion in glacier regions, 

 and in order to find out the law that rules the variation of glacial 

 erosion. Collecting and comparing the researches of different 

 scientists, we obtain the following list : 



Alaska, Muir Glacier 12 980 



Grœnland, Isortok River 9 744 



„ Alangordlek 2 374 



Iceland, Jokulsâ å Breiôamerkrsandi 1 876 



Jostedalsbræ, Langedalsbræ 523 



Hardangerjökel, Isdalsskaak 345,3 



Jotunheim, Leira 92,2 



The figures given in the above Hst, represent the number 

 of grams per cubic-metre of muddy river-water for maximum 

 erosion. We here observe a very stringent law of nature, viz. 

 maximum erosion is greatest in regions of greatest glaciation, 

 and, in a marked manner, is decreasing in rate, as, through 

 a series of different glacier regions, glaciation is diminishing 

 in intensity. 



When further extending our studies of glacial erosion to 

 cover the problem of its influence upon the detailed configuration 

 of the surface of glacier regions, it will prove highly useful to 

 introduce a fixed measure and a precise definition as regards 

 this phenomenon. Introducing the appellation of normal erosion, 

 this may be defined to be the rate of erosion parallel to the 

 normal of the plane of erosion. According to our present ex- 

 perience it is most convenient to calculate normal erosion by the 

 number of micro-millimetres a year. 



There are only a few numbers to be entered in the list, 

 but it is highly interesting to see that they are sufficient to prove 

 the very same law as was proved above to exist regarding the 

 amount of maximum erosion. Making a list of the very few 

 numbers, we obtain: 



