vi.] THE SLATES ON THE ROOF. 137 



France, in Sicily round Etna, in Italy round Vesuvius, 

 and in so many West Indian Islands ; the last confusion 

 of which is very likely to be this : 



That when the volcano has succeeded as it did in 

 the case of Sabrina Island off the Azores in 1811, and 

 as it did, perhaps often, in Snowdonia in piling up an 

 ash cone some hundred feet out of the sea ; that as 

 has happened to Sabrina Island the cone is sunk 

 again by earthquakes, and gnawn down at the same 

 time by the sea-waves, till nothing is left but a shoal 

 under water. But where have all its vast heaps of 

 ashes gone ? To be spread about over the bottom of 

 the sea, to mingle with the mud already there, and so 

 make beds of which, like many in Snowdon, we cannot 

 say whether they are of volcanic or of marine origin, 

 because they are of both. 



But what has all this to do with the slates ? 

 I shall not be surprised if my readers ask that 

 question two or three times during this paper. But 

 they must be kind enough to let me tell my story my 

 own way. The slates were not made in a day, and I 

 fear they cannot be explained in an hour : unless we 

 begin carefully at the beginning in order to end at the 

 end. Let me first make my readers clearly understand 

 that all our slate-bearing mountains, and most also of 

 the non-slate-bearing ones likewise, are formed after 

 the fashion which I have described, namely, beneath 

 the sea. I do not say that there may not have been, 

 again, and again, ash-cones rising above the surface of 

 the waves. But if so, they were washed away, again 

 and again, ages before the land assumed anything of 

 its present shape ; ages before the beds were twisted 

 and upheaved as they are now. 



