SUBTERRANEAN THUNDER. 



by their fright from bringing supplies into the markets 

 of the town, a famine commenced, and the power of the 

 authorities being at length overborne, a general flight ensued. 

 Nearly the whole population deserted the town, in which large 

 masses of the precious metals, the produce of the surrounding 

 mines, had been stored. Bands of plunderers lingered to seize 

 this treasure. After a while the inhabitants being familiarised 

 with the continuance of the subterraneous thunder, unaccompanied 

 by any other symptoms of earthquake, the more courageous 

 returned to the town and fought with the robbers in defence of 

 their property. 



In no part of the mountainous regions of Mexico was anything 

 of this kind ever before known or heard of, nor has it ever recurred 

 since. Thus it would appear, that as chasms in the inferior parts 

 of the crust of the earth are opened or closed, the sound produced 

 by the agitation of the igneous ocean, which roars beneath it, is 

 propagated or intercepted in different directions and at different 

 times. 



31. It would be a great mistake to assume that earthquakes are 

 always merely local phenomena of very limited range. On the 

 contrary, they have in some cases been manifested over a large 

 portion of the surface of the globe. The great earthquake by 

 which Lisbon was destroyed on the 1st November, 1755, was 

 felt over the whole extent of Europe, from the Alps to the coast of 

 Sweden, over Northern Germany and the shores of the Baltic, 

 across the Atlantic to the West Indies, where the shocks were 

 sensible in the islands of Barbadoes, Martinique, and Antigua, 

 and across the continent of North America to the great northern 

 lakes. 



Distant fountains were interrupted in their flow. Thus the hot 

 springs of Toplitz were first dried up but soon reappeared, sending 

 up unusual quantities of water of an ochreous colour.* 



32. That the solid surface of the bottom of the ocean shared in 

 the general undulation manifested over so great an extent of the 

 continents on this occasion could not be doubted, if no other 

 evidence of it existed save the transmission of the undulation 

 across the Atlantic. But we have more direct evidence of this in 

 the sudden changes of elevation of the water of the ocean itself. 

 At Cadiz the sea rose above sixty feet, and in the islands of 

 Barbadoes, Martinique, and Antigua, where the normal rise of 

 the tide does not much exceed two feet, the water suddenly rose 



* The fact that earthquakes had the effect of interrupting the flow of 

 springs was known to the ancients, and is noticed by Demetrius of 

 Oalatia, 



159 



