ORIGIN AND DEVELOPMENT OF ORE DEPOSITS. 149 



can not only mark out the true direction and position of the 

 faults with a great degree of accuracy, even when they have not 

 actually heen anywhere seen, but also, in most cases, determine 

 their inclination or underlie. The abrupt termination of the 

 Plymouth limestones to the westward, for instance, long ago 

 suggested to Sir Henry Delabeche ; the existence of one or more 

 N.S. faults with eastern underlie, somewhere in the neighbour- 

 hood of the Tamar, and the working of the mines in the 

 neighbourhood has fully shewn the accuracy of his views. 



