GEOLOGY. 271 



their function to counteract the levenin<^ effect of water, partly by 

 heaping up new matter in certain localities, and partly by deepen- 

 ing one portion, and forcing out another of the earth's envelope. 



In a paper, as profound in its views as it is luminous in its state- 

 ment, Sir John llerschel has indicated the philosophy of these di- 

 vulsions and upheavals, and we cannot do better here than epit- 

 omize his statement. The land, as has been seen, is perpetually 

 wearing down, and the materials are being carried out to sea, — 

 thinning towards the land, and thickening over all the bed of the 

 sea. What must happen ? If the continents be lightened, they 

 will rise ; if the bed of the sea receive additional weight, it will 

 sink. It is impossible but that this increase of pressure in some 

 places, and relief in others, must be very unequal in their bear- 

 ings ; so that at some place or other this solid floating crust must 

 be brought into a state of strain, and if there be a weak or a soft 

 place, a crack will at last take place. When this happens, the 

 land goes down on the heavy side, and up on the light side. Thi3 

 is exactly what happens in earthquakes. We should naturally ex- 

 pect that such cracks and outbreaks would occur along those lines 

 where the relief of pressure is the greatest, and also its increase 

 on the sea-side, that is to say, along or in the neighborhood of the 

 sea-coast, where the destruction of the land is going on with most 

 activity. Now, it is a remarkable fact in the history of volcanoes 

 that there is hardly an instance of any active volcano at any con- 

 siderable distance from the sea-coast, while it is to be observed 

 that the favorite sporting-places of earthquakes are the regions 

 covered by the great chains of volcanic cones. 



That earthquakes operate to raise the land-masses is not a mere 

 matter of speculation, but a fact of repeated observation. In 1822, 

 in a single night (Nov. 19), the whole coast line of Chili for a 

 hundred miles about Valparaiso, with the mighty chain of the 

 Andes, was hoisted at one shock from 2 to 7 feet above its former 

 level, leaving the beach below the old low-water mark high and 

 dry. In 1819, in an earthquake in India, in the District of Cutch, 

 bordering on the Indus, a tract of country more than 50 miles 

 long and 16 broad was suddenly raised 10 feet above its former 

 level. And again, in 1538, in the convulsion which threw up the 

 Monte Nuovo, the whole coast of Pozzuoli, near Naples, was 

 raised 20 feet above its former level, and remains so permanently 

 upheaved to this day. There are hundreds of the like instances 

 on record, and no doubt, when we come to get full scientific 

 accounts of the late convulsion, it will be found that parts of the 

 coast of South America have been raised above their former level. 



Such is the way in which earthquakes do their work, and they 

 are always at work. According to Humboldt, there is not a day 

 in which the earth is not shaken by these commotions ; so that the 

 state of perpetual movement is the normal condition of the sur- 

 face of our globe, and, if we had apparatus sufficiently sensitive, 

 we should doubtless detect this constant movement. And, indeed, 

 already astronomers complain that their instruments betray by in- 

 explicable perturbations the instability of the crust that supports 

 them. 



