EARTH QFATCES. 205 



and the subterranean thunder" (bramidos y truenos suiter- 

 raneos] of Guanaxuato.* This celebrated and rich mountain 

 city lies far removed from any active volcano. The noise 

 began about midnight, on the 9th of January, 1784, and con- 

 tinued for a month. I have been enabled to give a circum- 

 stantial description of it from the report of many witnesses, 

 and from the documents of the municipality, of which I was 

 allowed to make use. From the 13th to the 16th of January, 

 it seemed to the inhabitants as if heavy clouds lay beneath 

 their feet, from which issued alternate slow rolling sounds and 

 short quick claps of thunder. The noise abated as gradually as 

 it had begun. It was limited to a small space, and was not 

 heard in a basaltic district at the distance of a few miles. 

 Almost all the inhabitants in terror left the city, in which 

 large masses of silver ingots were stored, but the most cou- 

 rageous, and those more accustomed to subterranean thunder, 

 soon returned in order to drive off the bands of robbers who 



* On the Iramidos of Guanaxuato, see my Essai polit. sur la Nouv. 

 Espagne, t. i. p. 303. The subterranean noise, unaccompanied with any 

 appreciable shock, in the deep mines and on the surface (the to\vn of 

 Guanaxuato lies 6830 feet above the level of the sea) was not heard in 

 the neighbouring elevated plains, but only in the mountainous parts of 

 the Sierra, from the Cuesta de los Aguilares, near Marfil, to the north of 

 Santa Rosa. There were individual parts of the Sierra 24-28 miles 

 north-west of Guanaxuato, to the other side of Chichimequillo, near the 

 boiling spring of San Jose" de Comangillas, to which the waves of sound 

 did not extend. Extremely stringent measures were adopted by the 

 magistrates of the large mountain-towns, on the 14th of January, 1784, 

 when the terror produced by these subterranean thunders was at its 

 height. " The flight of a wealthy family shall be punished with a fine 

 of 1000 piastres, and that of a poor family with two months' imprison- 

 ment. The militia shall bring back the fugitives." One of the most 

 remarkable points about the whole affair is the opinion which the ma- 

 gistrates (el cabildo) cherished of their own superior knowledge. ID 

 one of their prodamas, I find the expression, " The magistrates, in their 

 wisdom, (en su sabiduria) will at once know when there is actual danger, 

 and will give orders for flight , for the present let processions be insti- 

 tuted." The terror excited by the tremor gave rise to a famine, since it 

 prevented the importation of corn from the table-lands, where it abounded. 

 The ancients were also aware that noises sometimes existed without 

 earthquakes; Aristot., Meteor., ii. p. 802; Plin., ii. 80. The singular 

 noise that was heard from March, 1822, to September, 1824, in the 

 Dalmatian island, Meleda, (sixteen miles from Eagusa,) and on which 

 Partsch has thrown much light, was occasionally accompanied by shock* 



