NOTES ON BRAZIL. 



7 



this internal furnace is not situated in the upper part of the mountain 

 is evident from the quantity of matter which has been discharged; 

 incomparably more massy than the mountain itself, perhaps than the 

 whole island ; for its shores exhibit, even to the water's edge, layers of 

 lava, some of them decomposed indeed, which seem, when ejected, 

 to have flowed far into the ocean, and now form its bed. That the 

 cauldron is much below the base of the mountain and the level of the 

 sea is probable, because the dome which covers it must be strong enough 

 to support the whole weight of the mountain ; and so far as I could 

 learn, the fiery mass collected there produces no perceptible effect upon 

 the waters of the ocean, nor upon the springs on shore. The length of 

 the chimney, too, cannot be less than the height of the mountain, and 

 if we estimate the weight of fluid lava at only three times that of water, 

 it will yield us a pressure upon the dome, tending to break it up, and 

 expose the furnace, of not less power than eighteen thousand pounds 

 to every square inch ; a pressure, however, which it must formerly have 

 sustained, or the crater could not have been raised so high. 



If allowed to guess at the magnitude of that mass of matter which 

 has been discharged, I should say that it cannot be less than thirty 

 cubic miles. Making every allowance, therefore, for the increase of 

 bulk by the action of fire, and for the absorption of water, we still find 

 a chasm, beneath the surface of the island, which almost confounds the 

 imagination. We cannot, indeed, suppose, although the word " dome" 

 has been used to describe its covering, that this chasm resembles a 

 hollow sphere, containing in its lower section the mass of liquid fire 

 which may still exist, while the upper one stretches above like a canopy ; 

 it probably consists of galleries, running between substantial buttresses, 

 capable of sustaining securel y the whole weight of the mountain ; 

 which indeed appears to be one of the most solid among isolated volcanos. 

 Is it unreasonable to suppose, that some of these galleries, in their 

 ramifications, may unite with those belonging to the Pico of Fayal, or 

 with that mass of fire which has manifested its existence near to St. 

 Michael's ? The question is interesting, and may attract attention. 



