EARTH WAVES OF COMMOTION.

In the city of Quito, which lies at the foot of a still active volcano (the Ruca Pichincha), and at an elevation of 9,540 feet above the level of the sea, which has beautiful cupolas, high vaulted churches, and massive edifices of several stories, I have often been astonished that the violence of the nocturnal earthquakes so seldom causes fissures in the walls; whilst in the Peruvian plains, oscillations, apparently much less intense, injure low reed cottages.

The natives, who have experienced many hundred earthquakes, believe that the difference depends less upon the length or shortness of the waves, and the slowness or rapidity of the horizontal vibrations, than on the uniformity of the motion in opposite directions.

The circling rotatory commotions are the most uncommon, but, at the same time, the most dangerous.

Walls were observed to be twisted, but not thrown down; rows of trees turned from their previous parallel direction; and fields, covered with different kinds of plants, found to be displaced in the great earthquake of Riobamba, in the province of Quito, on the 4th February, 1797, and in that of Calabria, between the 5th of February and the 28th of March, 1783.

The phenomenon of the inversion or displacement of fields and pieces of land, by which one is made to occupy the place of another, is connected with a translatory motion or penetration of separate terrestrial strata.

When I made the plan of the ruined town of Riobamba, one particular spot was pointed out to me, where all the furniture of one house had been found under the ruins of another.

The loose earth had evidently moved like a fluid in currents, which must be assumed to have been directed first downwards, then horizontally, and lastly upwards.

It was found necessary to appeal to the Audiencia, or Council of Justice, to decide upon the contentions that arose regarding the proprietorship of objects that had been removed to a distance of many hundred toises.—

Humboldt.