Ch. XIX.] LAKE OF MASAYA. 349 



erecting a steam purnp to raise the water for the supply 

 of the town. At the bottom of this section are seen great 

 cliffs of massive trachyte (No 1. in section). Above this 

 is an ash bed. then a bed of breccia containing; fragments of 



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trachyte, then another bed of cinders, which looks like a 



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rough sandstone, but is pisolitic, and contains pebbles of 

 the size of a bean. This bed is surmounted by one that 



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possesses great interest (No. 5 in section). It is composed 

 of fine tufa, in which is imbedded a great number of large 

 angular fragments of trachyte, some of which are more 



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than three feet in diameter. It is the last bed but one, 

 the surface being composed of lightly coherent strata of 

 tufaceous ash, worn into an undulating surface by the 

 action of the elements. 



I believe there is but one explanation possible of the 

 origin of these strata ; namely, that the great bed of 

 trachyte at the base is an ancient lava bed ; and that 

 this, perhaps, long after it was consolidated, was covered 

 by beds of ashes and sconce thrown out by a not far 

 distant volcano, and that at last a great convulsion broke 

 through the trachyte bed and hurled the fragments over 

 the country along with dense volumes of dust and ashes. 

 The angular blocks of trachyte imbedded in the stratum 

 No. 5 in section are exactly the same in composition as 

 the great bed below, and in them I think we see the 

 fragments of the rocks that once filled the perpendicular- 

 sided hollow now occupied by the lake. Looking at the 

 vast force required to hollow out the basin of the lake, by 

 blasting out the whole contents into the air, distributing 

 them over the country, so that they have not been piled 

 up in a volcanic cone round the vent, but lie in compa- 

 ratively level beds, I cannot expect that this explanation 



