204 COSMOS. 



of November, 1827, described by Boussingault, subterranean 

 detonations were heard in the whole valley .of Cauca during 

 twenty or thirty seconds, unattended by motion. The nature 

 of the noise varies also very much, being either rolling, or 

 rustling, or clanking like chains when moved, or like near 

 thunder, as, for instance, in the city of Quito ; or lastly, clear 

 and ringing, as if obsidian or some other vitrified masses were 

 struck in subterranean cavities. As solid bodies are excellent 

 conductors of sound, which is propagated in burnt clay, foi 

 instance, ten or twelve times quicker than in the air, the sub- 

 terranean noise may be heard at a great distance from the 

 place where it has originated. In Caracas, in the grassy 

 plains of Calabozo, and on the banks of the Rio Apure, which 

 falls into the Orinoco, a tremendously loud noise, resembling 

 thunder, was heard, unaccompanied by an earthquake, over a 

 district of land 9200 square miles in extent, on the 30th of 

 April, 1812, whilst at a distance of 632 miles to the north- 

 east, the volcano of St. Vincent in the small Antilles, poured 

 forth a copious stream of lava. With respect to distance, this 

 was as if an eruption of Vesuvius had been heard in the north 

 of France. In the year 1 744, on the great eruption of th 

 volcano of Cotopaxi, subterranean noises, resembling the dis- 

 charge of cannon, were heard in Honda, on the Magdalena 

 River. The crater of Cotopaxi lies not only 18,000 feet higher 

 than Honda, but these two points are separated by the colossal 

 mountain-chain of Quito, Pasto, and Popayan, no less than by 

 numerous valleys and clefts, and they are 436 miles apart. 

 The sound was certainly not propagated through the air, but 

 through the earth, and at a great depth. During the violent 

 earthquake of New Granada, in February, 1835, subterranean 

 thunder was heard simultaneously at Popayan, Bogota, Santa 

 Marta, and Caracas, (where it continued for seven hours without 

 any movement of the ground,) in Haiti, Jamaica, and on the 

 Lake of Nicaragua. 



These phenomena of sound when unattended by any per- 

 ceptible shocks, produce a peculiarly deep impression even on 

 persons who have lived in countries where the earth has been 

 frequently exposed to shocks. A striking and unparalleled 

 instance of uninterrupted subterranean noise, unaccompanied 

 by any trace of an earthquake, is the phenomenon known in 

 the Mexican elevated plateaux by the name of the " Roaring 



