vi.] THE SLATES ON THE EOOF. 133 



the fire, in wholesome fear of his own weakness and 

 ignorance, any puffs of mining companies which may 

 be sent him as one or two have probably been sent 

 him already. 



Furnished with which keys to the map, let him 

 begin to con it over, sure that there is if not an order, 

 still a grand meaning in all its seeming confusion; and 

 let him, if he be a courteous and grateful person, 

 return due thanks to Professor Ramsay for having 

 found it all out; not without wondering, as I have 

 often wondered, how even Professor Kamsay 's acuteness 

 and industry could find it all out. 



When my reader has studied awhile the confusion 

 for it is a true confusion of the different beds, he 

 will ask, or at least have a right to ask, what known 

 process of nature can have produced it ? How have 

 these various volcanic rocks, which he sees marked as 

 Felspathic Traps, Quartz Porphyries, Greenstones, and 

 so forth, got intermingled with beds which he is told 

 to believe are volcanic ashes, and those again with 

 fossil-bearing Silurian beds and Cambrian slates, which 

 he is told to believe were deposited under water? 

 And his puzzle will not be lessened when he is told 

 that, in some cases, as in that of the summit of 

 Snowdon, these very volcanic ashes contain fossil 

 shells. 



The best answer I can give is. to ask him to use 

 his imagination, or his common sense ; and to picture 

 to himself what must go on in the case of a submarine 

 eruption, such as broke out off the coast of Iceland in 

 1783 and 1830, off the Azores in 1811, and in our day 

 in more than one spot in the Pacific Ocean. 



A main bore or vent or more than one opens 



