These cones the Indians called ovens, and in many of them was long heard a subterranean noise resembling that of water briskly boiling.  Out of a great chasm in the midst of those ovens there were thrown up six larger elevations, the highest being 1,640 feet above the level of the plain, 4,315 above sea level, and now constituting the principal volcano of Jorullo.  The smallest of the six was 300 feet in height; the others of intermediate elevation.  The highest of these hills had on its summit a regular volcanic crater, whence there have been thrown up great quantities of dross and lava, containing fragments of older rocks.  The ashes were transported to immense distances, some of them having fallen on the houses at Queretaro, more than forty-eight leagues from Jorullo.  The volcano continued in this energetic state of activity for about four months; in the following years its eruptions became less frequent, but it still continues to emit volumes of vapor from the principal crater, as well as from many of the ovens in the upheaved ground.

EFFECT ON THE RIVERS

The two rivers, which disappeared on the first night of this great eruption, now pursue an underground course for about a mile and a quarter, and then reappear as hot springs, with a temperature of 126 degrees F.

This wonderful volcanic upheaval is all the more remarkable, from the inland situation of the plain on which it occurred, it being no less than 120 miles distant from the nearest ocean, while there is no other volcano nearer to it than 80 miles.  The activity of the ovens has now ceased, and portions of the upheaved plain on which they are situated have again been brought under cultivation, and the volcano is in a state of quiescence.

The crater of Popocatapetl, which towers to a height of 17,000 feet, is a vast circular basin, whose nearly vertical walls are in some parts of a pale rose tint, in others quite black.  The bottom contains several small fuming cones, whence arise vapors of changeable color, being successively red, yellow and white.  All round them are large deposits of sulphur, which are worked for mercantile purposes.

Orizaba has a little less lofty snow-clad peak.  This mountain was in brisk volcanic activity from 1545 to 1560, but has since then relapsed into a prolonged repose.  It was climbed, in 1856, by Baron Muller, to whose mind the crater appeared like the entrance to a lower world of horrible darkness.  He was struck with astonishment on contemplating the tremendous forces required to elevate and rend such enormous masses—­to melt them, and then pile them up like towers, until by cooling they became consolidated into their present forms.  The internal walls of the crater are in many places coated with sulphur, and at the bottom are several small volcanic craters.  At the time of his visit the summit was wholly covered with snow, but the Indians affirmed that hot vapors occasionally ascend from fissures in the rocks.  Since then others have reached its summit, among them Angelo Heilprin, the first to gaze into the crater of Mont Pelee after its eruption.