THE 



GEOLOGICAL MAGAZINE. 



No. LXXXVI.— AUGUST, 1871. 



L — On Volcanos.^ 



By Henry Woodward, F.G.S., F.Z.S., 

 of the British Museum. 



IN whatever part of the world we live we can readily discover, by- 

 ordinary observation, that there are two great forces constantly 

 occupied in remodelling its surface, from year to year, from century 

 to century. 



Little of what they are now doing can be noted by us in our life- 

 time, or even in the lifetime of our race ; but as they have ceaselessly 

 laboured since our planet came into existence, we can, by examining 

 the marks they left long since, find oiit what each is now doing, and 

 what they can achieve together, for then they are most potent. 



These two mighty forces, Upheaval and Denudation, are represented 

 by Fire and Water. 



"The gentle rain which cometh down from heaven" is ever 

 occupied in the task of washing away, grain by grain, the dry land, 

 and every brook and river ceaselessly carries on the same task ; 

 whilst the Sea, on every coast-line, aims at equality — like a roaring 

 Eepublican as he is — only, like the ordinary Eepublican, he seeks "to 

 level himself up " by the degradation of his neighbour, the Earth, 

 till it reaches a level no higher than his own. 



Indeed, if water acted as the servant of denudation only, the Earth 

 would have but a poor chance of keeping her head above water ; but 

 far down beneath the earth where dwell the dethroned Titans, and 

 where Vulcan forges the thunderbolts for Jupiter (so at least we 

 learnt at school), it seems undeniable that the temperature is so 

 exceedingly high that any water happening to lose its way (as water 

 is apt to do in the dark among so many chinks, crannies, and cracks), 

 and getting down beneath its proper level, is immediately seized by 

 fire, and before it can escape into the bright air it is compelled, as 

 steam, to lift earth- weights, which probably, when all are put to- 

 gether, amount to as much or even more than the drop of water 

 ever did above-ground in the service of denudation. 



What do we know of the interior of the earth ? How far has man 

 been able to pry into the inside of the great revolving ball upon the 

 outside of which he is being carried around in London at the rate of 

 600 miles per hour? 



1 A paper read before the Geologists' Association, April Ist, 1870. 



VOL. VUI.— NO. LXXXVI. 22 



