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Ch. XXVI.] 



DIKES IN THE VAL DEL BOVE. 



17 



Eig. 78. 



Tortuous veins of lava at Punto di Giumeuto, Etna. 



Bove, or near the two ancient centres of ernption before alluded 

 to as the axes of Trifoglietto and Mongibello. They continue 

 to abound throughout that zone of the mountain where 

 lateral eruptions are frequent, but below that level they 

 become extremely rare^ as in tlie valley of Calanna^ for 

 example, in which tlie section of the Yal del Bove is continued. 

 Still lower in the same easterly direction, as in the valley of 

 San Giacomo for example, none occnr. The rarity or ab- 

 sence of dikes as we recede from the great centres of ernption, 

 is precisely what we might have expected if the vertical 

 fissures now filled with 

 solid rock were once 

 the channels which 

 gave passage to lava 

 currents. Some of the 

 dikes blend at their 

 termination upwards 

 with currents of lava, so 

 that they stop short in 

 their vertical direction, 

 and do not cut through the higher currents of lava which 

 were of a date posterior to the dikes. 



r 



We know not how large a quantity of modern lava may 

 have been poured into the bottom of the Val del Bove, yet 

 we perceive that eruptions breaking forth near the centre of 

 Etna have already made no small progress in filling up this 

 great hollow. Even within the memory of persons now 

 living, the rocks of Musara and Capra have, as before stated, 

 lost much of their height and picturesque grandeur by the 

 piling up of recent lavas round their base, and the great 

 chasm has intercepted many streams which would otherwise 

 have deluged the fertile region below. The volcanic forces 

 are now labouring, therefore, to repair the breach caused pro- 

 bably by one or more paroxysmal eruptions of ancient date 

 on one side of the great cone ; and unless their energy should 

 decline, or a new sinking take place, they may in time efface 

 this inequality. In that event, the restored portion will 

 always be unconformable to the more ancient part, yet it 

 will consist, like it, of alternating beds of lava and scorise. 



VOL. II, 



c 



