COAL AT DOVER. 243 



Society of London his views on this subject, and 

 declared his belief in the existence of the valued 

 mineral below rocks from which the coal was ordinarily 

 presumed to be separated by many thousands of feet 

 of different rocks. To enable us to understand the 

 bold nature of this speculation of Mr. Austen's, we 

 require to bear in mind the teachings of geology con- 

 cerning the succession of the rocks which compose 

 the crust of our earth. 



First of all, let us note that the various ages or 

 periods into which time past has been mapped out by 

 geologists, correspond to or with as many groups of 

 rocks, each marked by its own special structure, fossils, 

 and other characteristics. Then, in the second place, 

 we have to bear in mind that the order in which one 

 rock-formation succeeds another never alters. Take 

 as an example of this stable order of the rocks the 

 following : the Coal rocks, in their natural order, lie 

 above the Devonian or Old Red Sandstone, while, in 

 turn, they are overlaid by the Permian rocks. 



Thus, if we could see in any district a section 

 showing the complete thicknesses of these three rock- 

 formations as they were deposited, we should find the 

 oldest or Devonian strata lying lowest, the Coal in the 

 middle, and the Permian above the Coal, this last for- 

 mation being the youngest or most recently formed 

 of the three. Suppose, further, that a person on 

 whose estate the Devonian rocks came to the surface 

 consulted a mining engineer as to the probability of 

 coal being found beneath the soil of his possessions, 

 it is very clear what the reply of the scientist would 

 be. He would say that as the Coal is a younger rock 

 than the Devonian, and was therefore formed after the 

 latter, and as it lies in its natural order above the 



