ON THE RIVERS AND CREEKS. 189 



doubtedly worn away by the continual wash, as 

 may be seen from their rounded surfaces, but 

 otherwise they may be considered almost ever- 

 lasting. In the old creek beds they are found in 

 the midst of the sand, clay, and pebbles, even then 

 often preserved for an indefinite period, although 

 becoming brittle, and even soft, in a porous soil. 

 From borings made in the alluvion of the coast it 

 has been found that this semi-fossil wood still 

 remains undecomposed at depths of over a hun- 

 dred feet, being only reduced to its elements when 

 brought to the surface. 



As development is only possible through a 

 multitude of generations, the work of the river and 

 creek is of the utmost importance. There must 

 be destruction to make room for new individuals. 

 Without this the same trees would live on for ages, 

 and once the forest was occupied no room could be 

 found for a single seedling. When, therefore, we 

 see that the country is intersected with such a 

 multitude of streams, and that these are continually 

 changing their courses more or less, at each slight 

 alteration giving an opportunity for some new 

 seedling to come to the front, we can understand 

 why species are by no means at a standstill. 

 Instead of stagnation there are continual changes 

 taking place, and it may be safely affirmed that 



