SUBTERRANEAN NOISES.

The most striking instance of uninterrupted subterranean noise unaccompanied by any trace of earthquake, is the phænomenon which is known in the Mexican territory by the name of “the subterranean roaring and thundering (bramidos y truenos subterraneos) of Guanaxuato.”

This rich and celebrated mountain-city is situated at a distance from any active volcano.

The noise began on the 9th January, 1784, at midnight, and lasted above a month.

I have been enabled to give a circumstantial description of the phænomenon from the report of many witnesses, and from the documents of the municipality which I was permitted to make use of.

From the 13th to the 16th of January, it was as if there were heavy storm-clouds under the feet of the inhabitants, in which slow rolling thunder alternated with short thunder-claps.

The noise ceased gradually, as it had commenced; it was confined to a small space, for it was not heard in a basaltic district at the distance of only a few miles.

Almost all the inhabitants were terrified and quitted the city, in which large masses of silver were stored; but the most courageous, when they had become somewhat accustomed to the subterranean thunder, returned and fought with the bands of robbers who had taken possession of the treasure.

Neither at the surface, nor in mines 1,598 English feet in depth, could the slightest trembling of the ground be perceived.

In no part of the whole mountainous country of Mexico had anything similar ever been known before; nor has this awful phænomenon been since repeated.

Thus, as chasms in the interior of the earth close or open, the propagation of the waves of sound is either arrested in its progress or continued until it reaches the ear.—Humboldt’s Cosmos.