EARTHQUAKE. 



more from the lava and ashes than earth- 

 quakes. 



If stronger proofs were necessary, that 

 volcanic eruptions cause this phenome- 

 non, the rising of hills near ./Etna, or any 

 other volcano, and the Lipari Islands, are 

 sufficient demonstrations how severely 

 the earth must be convulsed by subter- 

 raneous tires ; those consequences are 

 not, however, always visible, earthquakes 

 often occurring without any other effect 

 than the overturning of slightly built 

 edifices, an undulating or shaking motion, 

 and a deadened sound ; but it by no 

 means follows that the origin of such 

 were not to be attributed to tire, the va- 

 pours caused by which may roll through 

 cavities, actually p^ss from a very great 

 distance to a volcanic mountain, or es- 

 cape unperceived through the sea or ob- 

 scure vents. 



The electric fluid being known to reside 

 in the earth in very considerable quan- 

 tities, and always seeking an equilibrium, 

 great abundance may sometimes collect 

 through various causes in a particular 

 spot, whence it will be attracted to ano- 

 ther less charged with this astonishing 

 fluid; when the tremendous conflict be- 

 tween it and the air is remembered dur- 

 ing a storm in our atmosphere, we must 

 readily admit that it may produce a strong 

 concussion in the earth, and probably 

 be the origin of the slight earthquakes 

 peculiar to some countries. 



Another cause of inconsiderable tremb- 

 lings may, perhaps, proceed from the ope- 

 rations ot subterraneous streams, which 

 rushing through caverns, ar.d undermin- 

 ing vast bodies of earth and stone, those 

 fall and shake the neighbouring parts in 

 proportion to their bulk and weight. 

 When the motion of the sea, during an 

 earthquake, had destroyed the support 

 of Port Royal, in Jamaica, the town sunk 

 into it ; in the same manner new cavities 

 occurring through the fall of earth, the 

 surface must necessarily sink in the same 

 degree, if it is within the influence of the 

 cause. 



Frezier is of opinion that earthquakes 

 should be ascribed to an effect of the wa- 

 ters, which appear to moisten the earth, 

 in passages similar to the veins of living 

 bodies. Now the waters may occasion 

 earthquakes after several manners, either 

 by dissolving the salt scattered through 

 the earth, or by penetrating through po- 

 rous lands, mixed with stones, which they 

 insensibly loosen ; and the fall or removal 

 thereof must cause a stroke orshock, such 

 as is felt in earthquakes. I .as! ly, t he wa- 



VOL IV 



ter penetrating some sulphurous bodies 

 must there cause a fermentation, and then 

 the heat produces foul exhalations, which 

 infect the air when they open the earth." 



This extract from a narrative of the 

 dreadful earthquakes at Lima in 1746, is 

 illustrated by the experiment of M. Le- 

 mery, related in the memoirs of the 

 French Academy ot Sciences for 1700 ; 

 that gentleman having mixed equal quan- 

 tities of filings of iron and sulphur, and 

 tempered them with water into the con- 

 sistence of paste, buried tliem ; they 

 some time afterwards agitated the earth, 

 and finally burst into a flame. To con- 

 firm this effect of fire, however generated 

 in the bowels of the earth, we shall quote 

 the following paragraph from that accu- 

 rate modern observer Spalianzani, who 

 was indebted to Professor Bottis for the 

 facts contained in it, winch rejate to the 

 production of seven small mountains by 

 the eruption of Vesuvius in 1760. After 

 repeated concussions of the earth, which 

 were felt fifteen miles round Vesuvius, 

 the sides of the fiery mountain opened in 

 the territory of the Torre del Greco, and 

 fifteen volcanos appeared, eight of which 

 were soon after covered by a torrent of 

 lava, which rushed from one of them ; 

 the other seven remaining entire, and 

 incessantly ejecting from their mouths 

 vast quantities of ignited substances, 

 which falling almost perpendicularly 

 around the volcanos, produced, in the 

 short space of ten days, seven small 

 mountains, of various heights, disposed 

 in a right line. During these ejections, 

 the noise which accompanied them some- 

 times resembled that of violent thunder, 

 and at others the discharge of a number of 

 cannons. Several of the burning stones, 

 even the largest, were thrown to the 

 height of 960 feet, and some fell at a 

 considerable distance from the mouths 

 whence they were thrown. These eruc- 

 tations shook all the neighbouring coun- 

 try, and the roarings of the mountain 

 were dreadful to the inhabitants. 



That there are many substances exist- 

 ing within the depth of the earth, which, 

 coalesced, produce fire, cannot be disput- 

 ed, but that they exist in such amazing 

 quantities as to afford fire for centuries, 

 seems at least probemat ical ; there is 

 therefore but tw ways of accounting for 

 their continuance, either that the volatile 

 effluvia of the ignited matter, collected 

 on the sides of volcanic caverns, becomes 

 new fuel; or that heat being necessary 

 for the various properties of the globe, a 

 ^tent fire, coeval with the creation, 



NB 



