1 92 1. No. 1 1. 



THF STRAXnFLAT AND ISOSTASY, 



35 



Fig. 1 6. Shore-ledge cut in gabbro with bands of syenite, at Simalanga, 

 Kvænangen Fjord [after a photograph by T. Vogt]. 



A more convincing demonstration of the manner in which the shore-erosion 

 by frost actually works, could hardly be found. 



The ledges are 8 and 12 metres broad, the one is cut in gabbro with 

 bands of syenite (Fig. 16), the other in dolomite. Their outer edges rise 

 generally between half a metre and one metre, or a little more, above the 

 level of their floor inside, which lies perhaps half a metre above the upper 

 fucus limit, and slightly above average high-tide level. The floor of the 

 ledges may probably be flooded at spring-tide. 



As A^ogt maintains, these ledges are obviously formed by frost dis- 

 integration in recent time and at present sea-level. He thinks that the 

 eroding work has to a great extent been performed by accumulations of 

 snow on the ledges, which have frequently been soaked with spray from 

 the waves, and have afterwards been frozen. In this manner he finds an 

 explanation of the height of the ledges above the average high-tide level. 

 I think, however, that it is the alternate melting and freezing of the ice 

 and snow accumulated on the ledges, which have had the chief erosive 

 effect on the rock in the manner described on a preceding page. The ice has 

 been formed on the ledges at spring-flood and at exceptional high water, 

 as well as by water washed up by the waves in cold weather, and on top of 

 this ice snow-drifts have been accumulated (cf. Fig. 14). Because of the 

 salt contained in the sea-water the soaking of the snow by the spray from 

 the waves may reduce somewhat the disintegrating effect of the melting 

 and freezing snow. 



