256 REACTION OF THE INTERIOR OF THE EARTH 



nate, broke forth eleven years later than the volcano 

 of Jorullo in the interior of Mexico. Both outbreaks 

 took place in cultivated plains, and after several 

 months of earthquakes and of subterranean " roarings " 

 (bramidos). In the Llano de Izalco a conical hill was 

 upheaved ; and contemporaneously with its upheaval a 

 stream of lava began to pour forth from its summit. 

 This was on the 23rd of February 1770. It is still 

 uncertain how much of its rapidly increasing height 

 should be attributed to " upheaval of the ground," and 

 how much to " accumulation " of erupted scoriae, ashes, 

 and masses of tufa ; but it is certain that, instead of 

 soon becoming extinct like Jorullo, the volcano of Izalco 

 has continued, ever since its first appearance, in uninter- 

 rupted activity, and often serves as a lighthouse to 

 mariners making the land in the Bay of Acajutla. Four 

 eruptions of flame are reckoned to take place in an 

 hour ; and the great regularity of the phenomenon has 

 astonished the few accurate observers who have wit- 

 nessed it. ( 38 ) The strength of the eruptions varied, 

 but not the time at which each took place. The height 

 attained by the volcano of Izalco was estimated after 

 the last great eruption, of 1825, at about 1600 feet, 

 nearly equal to the height of Jorullo above the original 

 cultivated plain from which it rose, but almost four 

 times as great as the crater of elevation in the Phle- 

 grsean Fields, called the Monte Nuovo, to which Scac- 

 chi ( 381 ) assigns, by exact measurement, 43 1|- feet. The 

 permanent activity of the volcano of Izalco, which was 

 long regarded as a safety-valve for the country round 

 San Salvador, did not, however, preserve the town from 

 complete destruction on Easter night in 1854. 



