Geology of Guatemala and Salvador. 457 



distances of 1500 and 2000 miles. Showers of ashes were dis- 

 tributed over the surface of the continent and both adjoining oceans, 

 through a space of the same prodigious diameter, reaching as far as 

 Jamaica to the north, and Bogota to the south. The enormous 

 crater produced by this evisceration of the mountain measures at 

 least six miles in diameter, being one of the largest known — cer- 

 tainly among those the date of whose formation is recorded and 

 unquestionable. The external slopes which reach to the sea, from 

 which the mountain rises as an almost insular promontory, are 

 composed of the larger blocks of lava and scorise thrown up by the 

 eruption. Within the Bay of Fonseca, the Isle of Tigre presents 

 a very regular cone, breached on one side, and composed of basaltic 

 lava and scoria3. On the opposite horn of the bay to that of Co- 

 seguina stands the volcanic cone of Conchagua, likewise basaltic, but 

 shewing no crater at the time of our authors' visit. It has very 

 recently broken out in eruption (February, 1868). A few leagues to 

 the west the volcanic cone of San Miguel, 7000 feet in height, was 

 in eruption in 1849, and discharged a stream of basaltic lava from 

 an opening very near the summit. Its previous eruptions had been 

 frequent, and many other lava streams have descended from it. It 

 has a deep circular crater, about three miles in circumference, with 

 perpendicular walls of solid rock, chiefly basaltic, as are the scoria 

 scattered about, but containing many small felspar crystals. 



Westward of San Miguel are several smaller volcanic cones, and 

 many very active mud volcanos discharging hot vapours, called by 

 the significant name of the " Infernillos." Next comes the ap- 

 parently extinct volcano of St. Salvador, having a lake within its 

 crater of a mile and a-half in diameter. It is surrounded by immense 

 accumulations of pumice-conglomerate. Further to the west rises 

 the volcanic cone of Izalco, remarkable from having been thrown up 

 on a spot which was before a level plain, by eruptions of lava and 

 scoriee, which, beginning in the year 1770, have lasted almost 

 without intermission down to the present time. The height of the 

 cone which, of coiu^se, is continually increasing, was, at the time of 

 our author's visit in 1864 above 10,000 feet. Its lavas are basaltic, 

 i.e., pyroxenic, of deep black colour, and highly vitreous, with 

 numerous crystals of glassy felspar and grains of olivine. Our 

 authors ascended it, and found at the summit a vast elliptic crater, 

 or rather three craters together, on a line corresponding with the 

 general volcanic axis of the district. The central crater gave out 

 much vapour from several fissures, especially from one deep and 

 large hole, within which almost continuous detonations were heard. 

 The vapours were chiefly steam, with a mixture of chlorydric and 

 sulphuric acids. 



Proceeding further westwards, after passing several smaller 

 volcanic cones, mostly extinct, and other numerous mud-volcanos, 

 we come to the very remarkable group of Pacaya and the volcanos 

 of Fuego and Aqua (fire and water) , near the lake of Amatitlan. 

 The first of these consists of several mountainous masses of trachyte, 

 embracing: a number of scorice-cones and craters. The highest of 



