CHAPTEK XIII. 



THE GEOLOGICAL HISTORY OF THE COLONY. 



THE further back one looks into past times the more 

 difficult it is, on the whole, to interpret the story con- 

 cealed by the rocks of any country. The reason of this 

 is that the older the formations are, the longer have 

 they been subjected to forces which tend to bring about 

 changes in rocks below ground and to sweep them away 

 and deposit their fragments elsewhere when exposed at 

 the surface ; in the first case their original characters 

 may be altered beyond recognition, and in the second 

 they may be entirely removed over large areas. 



In Cape Colony a very important class of evidence, 

 that of the fossil remains of plants and animals, can 

 only be brought to bear on the question at a compara- 

 tively late stage in the geological time-scale, viz., the 

 Devonian. In other countries the distribution of land 

 and water can to some extent be made out by means 

 of fossils from the Cambrian, Ordovician, and Silurian 

 systems, which together represent a great period of time 

 anterior to the Devonian. 



In all the other continents, however, there are rocks 

 older than the Cambrian whose characters show that 

 they were formed under conditions not very different 

 from those of to-day, and as yet these Pre-Cambrian 



419 27 * 



