THE WEST INDIAN BRIDGE. 



15 



Plate I, when the newly formed bay gradually becomes filled 

 with mud or the washes of the land. 



Valleys even in mountain regions are almost independent of i\^ 

 undulations of the strata, in that the courses of the streams fre- 



quently occupy the crests of folds, while the geological troughs are 

 represented by features in bold relief, as is illustrated in Fig. 3. It 

 is easily shown that valleys, even among mountains, whether parallel 



