CHAPTER V 



The key of the past, as of the present, is to be sought in the 

 present ; and, only when known causes of change have been 

 shown to be insufficient, have we any right to have recourse 

 to unknown causes. HUXLEY. 



More about fossil plants. The relation between rocks and scenery. 

 Rocks formed as sediment under water and rocks that are volcanic. 

 Dykes of basalt. The loneliness of a Greenland beach. Deserted 

 Settlements. 



'ANY of the localities visited were on un- 

 inhabited coasts where the land rose 

 gradually inland for a few hundred yards ; then the 

 gradient rapidly increased up the face of the 

 mountain. Deep ravines laid bare a succession of 

 sedimentary strata 1000 ft. or more in thickness 

 over which had been piled layer after layer of 

 lava-flows and beds of volcanic ash (Fig. 34). 

 Masses of frozen snow powdered with wind-blown 

 sand or the darker dust from the shales were often 

 met with in more shaded parts of the valleys. The 

 widely spread sheets of basalt, in some places as 

 many as thirty superposed layers, which give a 

 terraced appearance to the weathered face of the 

 cliffs like that on the rocks of Mull and other 

 islands off the west coast of Scotland, are proof of 

 long-continued volcanic activity on a stupendous 

 scale. Another expression of the same kind of 

 phenomenon is seen in the numerous dykes which 

 frequently cut across the beds of sandstone and 

 shale. A dyke consists of some igneous rock, 



