C24 



FLUID LAVA. 



[Ch. XXV. 



in which it acted upon the lava, I should say that it was like 

 a loaf of bread thrown into a bowl of very thick honey, which 

 gradually involves itself in the heavy liquid, and then slowly 



sinks to the bottom. 



' The lava, at a small distance from its source, acquires a 

 darker tint upon its surface, is less easily acted upon, and, as 

 the stream widens, the surface, having lost its state of per- 

 fect solution, grows harder and harder, and cracks into in- 

 numerable fragments of very porous matter, to which they 

 o-ive the name of scoriae, and the appearance of which has 

 led many to suppose that it proceeded thus from the moun- 

 tain. There is, however, no truth in this. All lava, at its 

 first exit from its native volcano, flows out in a liquid state, 

 and all equally in fusion. The appearance of the scoria? is to 

 be attributed only to the action of the external air, and not 

 +^ a-mr AHfe-ronm in the materials which compose it, since any 



om 



immediately 



its form. As we proceeded downward, 

 and more evident ; and the same lava 

 which at its original source flowed in perfect solution, un- 



more 



divided, and free from 



of any kind, a little 



farther down had its surface loaded with the scoriae in such 



manner 



tain, the whole current resembled nothing so much as a heap 

 of unconnected cinders from an iron-foundry.' In another 

 place he says, that ' the rivers of lava in the plain resembled 

 a vast heap of cinders, or the scoriae of an iron-foundry, roll- 

 ing slowly along, and falling with a rattling noise over one 



another.'"* Yon 



M 



j. 



Humboldt and Gay-Lussac, describes the lava of 1805 (the 

 most fluid on record) as shooting suddenly before their eyes 

 from top to bottom of the cone in one single instant. Pro 

 fessor J. D. Forbes remarks that the length of the slope c 

 the cone proper being about 1,300 feet, this motion 

 correspond to a velocity of many hundred feet in a few 

 seconds, without interpreting Von Buch's expression literally. 

 The same lava, when it reached the level road at Torre del 



* Otter's Life of Dr. Clarke. 



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