Vol. LI.] PHILOSOPHICAL TRANSACTIONS, 4^7 



more extensive fire under the sea, spread itself from thence, and as it passed in 

 places where the roof over it was naturally much thinner, as well as greatly 

 weakened by the undermining of these fires, it opened itself a passage and burst 

 forth. 



As the most extensive earthquakes generally proceed from the lowest countries, 

 but especially from the sea, so those of a smaller extent are generally found 

 among the mountains: hence it almost always happens that earthquakes which 

 are felt near the sea, if at all violent, are felt also in the higher lands; whereas 

 there are many among the hills, and those very violent ones, which never ex- 

 tend themselves to the lower countries. Thus we are told that at Jamaica 

 " shakes often happen in the country, not felt at Port Royal: and sometimes are 

 felt by those that live in and at the foot of the mountains, and by nobody else," 

 On the other hand, the earthquake that destroyed Port Royal extended itself all 

 over the island: and the same was observed of a smaller earthquake that hap- 

 pened there in 1 687-8; which latter undoubtedly came from the sea, as appears 

 by Sir Hans Sloane's account of it. 



Earthquakes of small extent are also very common among the mountains of 

 Peru and Chili. Antonio d'Ulloa says, " Whilst we were preparing for our de- 

 parture from the mountain Chichi-Choco, there was an earthquake which was 

 felt 4 leagues round about: our field tent was tossed to and fro by it, and the 

 earth had a motion like that of waves; this earthquake however was one of the 

 smallest that commonly happen in that country." The same author tells us, in 

 another place, that " during his stay at the city of Quito, or in the neigh- 

 bourhood of it, there were two earthquakes, violent enough to overturn some 

 houses in the country, which buried several persons under their ruins." 



Sect. 5. — It is generally found that earthquakes in hilly countries are much 

 more violent than those which happen elsewhere; and this is observed to be 

 the case, as well when they take their rise from the lower countries as among 

 the hills themselves. This appearance being so easily to be accounted for, from 

 the structure of the earth already described, Mr. M. contents himself with esta- 

 blishing the certainty of a fact which tends so greatly to confirm it. 



The earthquakes that have infested some of the towns in the neighbourhood 

 of Quito, have not only been incomparably more violent than that which de- 

 stroyed Lisbon, but they seem to have exceeded that also which destroyed Lima 

 and Callao. In Lisbon, many of the houses were left standing, though few of 

 them were less than 4 or 5 stories high. At Lima also, it is only said that *' all 

 the buildings, great and small, or at least the greatest part of them, were de- 

 stroyed." Callao likewise, as it appears from the accounts we have of it, had 

 many houses left unhurt by the earthquake, till the wave came which over- 

 whelmed the whole town, and threw down every thing that lay in its way. All 



3 o2 



