A NEW THEORY OF VOLCANOES. 205 



transformed into heat, by which, at the places where the process goes 

 on with greatest energy, "the material of the rock so crushed and of 

 that adjacent to it are heated even to fusion. The access of water to 

 such points determines volcanic eruption." 



Now, all this is not mere theorizing. Mr. Mallet does not come 

 befoi - e the scientific world with an ingenious speculation, which may 

 or may not be confirmed by observation and experiment. He has 

 measured and weighed the forces of which he speaks. He is able to 

 tell precisely what proportion of the actual energy which must be de- 

 veloped as the earth contracts is necessary for the production of ob- 

 served volcanic phenomena. It is probable that nine-tenths of those 

 who have read these lines would be disposed to think that the con- 

 traction of the earth must be far too slow to produce effects so stu- 

 pendous as those which we recognize in the volcano and the earth- 

 quake. But Mr. Mallet is able to show, by calculations which cannot 

 be disputed, that less than one-fourth of the heat at present annually 

 lost by the earth is sufficient to account for the total annual volcanic 

 action, according to the best data at present in our possession. 



This would clearly not be the place to follow out Mr. Mallet's ad- 

 mirable theory into all its details. We must content ourselves with 

 pointing out how excellently it accouuts for certain peculiarities of the 

 earth's surface-configuration. Few that have studied carefully-drawn 

 charts of the chief mountain-ranges can have failed to notice that the 

 arrangement of these ranges does not accord with the idea of upheaval 

 through the action of internal forces. But it will be at once recog- 

 nized that the aspect of the mountain-ranges accords exactly with 

 what would be expected to result from such a process of contraction 

 as Mr. Mallet has indicated. The shrivelled skin of an apple affords 

 no inapt representation of the corrugated surface of our earth,. and, 

 according to the new theory, the shrivelling of such a skin is precisely 

 analogous to the processes at work upon the earth when mountain- 

 ranges were being formed. Again, there are few students of geology 

 who have not found a source of perplexity in the foldings and over- 

 lappings of strata in mountainous regions. No forces of upheaval 

 seem competent to produce this arrangement. But by the new theory 

 this feature of the earth's surface is at once explained ; indeed, no 

 other arrangement could be looked for. 



It is worthy of notice that Mr. Mallet's theory of volcanic energy 

 is completely opposed to ordinary ideas respecting earthquakes and 

 volcanoes. We have been accustomed vaguely to regard these phe- 

 nomena as due to the eruptive outbursting power of the earth's inte- 

 rior; we shall now have to consider them as due to the subsidence 

 and shrinkage of the earth's exterior. Mountains have not been up- 

 heaved, but valleys have sunk down. And in another respect the new 

 theory tends to modify views which have been generally entertained 

 in recent times. Our most eminent geologists have taught that the 



