THE EARTH. 4? 



curiously ^nployed in their consideration. Woodward has ascribed 

 the cause to a stoppage of the waters below the earth's surface by some 

 accident. These being thus accumulated, and yet acted upon by fires, 

 which he supposes still deeper, both contribute to heave up the earth 

 uoon their bosom. This, he thinks, accounts for the lakes of water 

 pioduced in an earthquake, as well as for the fires that sometimes 

 burst from the earth's surface upon those dreadful occasions. There 

 are others still who have supposed that the earth may be itse'f the 

 cause of its own convulsions. u When," say they, " the roots or basis 

 of some large tract is worn away by a fluid underneath, the earth sink- 

 ing therein, its weight occasions a tremor of the adjacent parts, some- 

 times producing a noise, and sometimes an inundation of water." Not 

 to tire the reader with a history of opinions instead of facts, some 

 have ascribed them to electricity, and some to the same causes that 

 produce thunder. 



It would be tedious, therefore, to give ail the various opinions that 

 have employed the speculative upon this subject. The activity of the 

 internal heat seems alone sufficient to account for every appearance 

 that attends these tremendous irregularities of nature. To conceive 

 this distinctly, let us suppose, at some vast distance under the earthj 

 large quantities of inflammable matter, pyrites, bitumens, and marca- 

 sites, disposed, and only waiting for the aspersion of water, or the 

 humidity of the air, to put their fires in motion : at last, this dreadful 

 mixture arrives ; waters find their way into those depths, through the 

 perpendicular fissures; or air insinuates itself through the same minute 

 apertures : instantly new appearances ensue ; those substances, which 

 for ages before lay dormant, now conceive new apparent qualities; 

 they grow hot, produce new air, and only want room for expansion. 

 However, the narrow apertures by which the air or water had at first 

 admission, are now closed up; yet as new air is continually generated, 

 and as the heat every moment gives this air new elasticity, it at length 

 bursts, and dilates all round ; and, in its struggles to get free, throws 

 all above it into similar convulsions. Thus an earthquake is produced, 

 more or less extensive, according to the depth or the greatness of the 

 cause. 



But before we proceed with the causes, let us take a short view 

 jf the appearances which have attended the most remarkable earth- 

 quakes. By these we shall see how far the theorist corresponds with 

 the historian. The greatest we find in antiquity is that mentioned by 

 Pliny,* in which twelve cities in Asia Minor were swallowed up in 

 one night: he tells us also of another, near the lake Thrasymene, 

 which was not perceived by the armies of the Carthaginians and Ro- 

 mans, that were then engaged near that lake, although it shook the 

 greatest part of Italy. Jn another placet he gives the following ac- . 

 count of an earthquake of an extraordinary kind. " When Lucius 

 Marcus and Sextus Julius were consuls, there appeared a very strange 

 prodigy of the earth, (as I have read in the books of ./Etruscan disci- 

 pline) "which happened in the province of Mutina. Two mountains 

 shocked against each other, approaching and retiring with the most 



* Pl'n lib. ii. cap. 86. f Ibid. lib. hi. cap. 85. 



voi. i. D 



