VAUX VOLCANIC ROCKS OF ICELAND. 



143 



Few, if any, countries present us with sucli remarkable or various 

 manifestations of the potency of subterranean heat as Iceland. So 

 much so, indeed, that it appears as though it were the acknowledged 

 safety-valve, in this portion of our globe at least, through which the 

 troubled contents of depths unknown may, on any emergency, find a 

 ready vent. 



Interest more than ordinary appears to have been taken of late in 

 this most remarkable region. Ko less than six parties of tourists 

 having, during the year before last, investigated the natural marvels 

 of the island. One of these adventurers, Lord Dufferin, in a most 

 interesting and amusing book, has given to the world a record of his 

 travels. Prom his " Letters from High Latitudes " we propose to 

 quote his graphic picture of the result of volcanic action, in producing 

 a very remarkable and very manifest change in the aspect of the large 

 tract of country to which that portion of his narrative refers. 



But before we proceed to this, it may perhaps be useful to recal to 

 the reader's recollection the two theories which have, up to the present 

 time, been put forth with respect to the causes of internal heat, and 

 hence to the origin of volcanic action in general. 



Some Geologists are of opinion that the interior of our globe has ever 

 been, and still is, in a state of fusion. The result of experiments, 

 indicating that in mines the temperature increases gradually with their 

 depth, has led to the idea that in the same ratio the temperature must 

 increase the nearer we approach the centre of the earth. Assuming 

 this to be the case, it is calculated that at a depth of fifty miles from 

 the surface the heat would be about double that of molten iron ; and the 

 natural difficulty which arises in consequence is this : "What would become 

 of the crust of the earth if it confined within it such a mass of fused 

 matter as would be the case if this were true ? Other scientific men 

 would rather refer these volcanic disturbances to heat generated by 

 ever-varying chemical changes which are taking place in the bowels of 

 the earth. This theory also is by no means free from difficulties ; 

 and it is probable that, in its present state, science is incapable of 

 fully drawing aside the veil, and revealing to our view the true 

 solution of the problem. 



"We will now, without more ado, introduce our readers to Lord Duf- 

 ferin, and beg them to imagine his party landed at E-eykjavik, a sea- 



