Ch. Vn. so UTFI AMERICA. S5 



matter was not totally exhaufted, nor the caufe of 

 the fhocks abfolutely removed. 



The frequent earthquakes to which fouth Ame- 

 rica, particularly Lima, and all the country of 

 Valles is fubject, opens a field for enquiry not lefs 

 ample than that juft mentioned, concerning their 

 caufes. Many hypothefes have been formed by 

 philofophers ; but the generality, and with the 

 ^reateft appearance of truth, agree in deducing them 

 principally from the violent force of the air con- 

 tained in fulphureous fubftances and other minerals, 

 and alfo that confined in the pores of the earth ; 

 which being too much coBipreiTed by the incumbent 

 •load, make a very violent refiilance. This is fo far 

 from implying any contradiction, that befides being 

 countenanced by reafon, it is alfo confirmed by expe- 

 rience» But the apparent difficulty confiils in ex- 

 plainiag how the vents of the earth become again 

 iilled with air, after one concuflion has happened ; 

 it being natural to think, that the quantity which 

 ilruggled for vent, was thereby difcharged, and 

 that a long interval of time was neceffary before 

 another could be produced. Alfo why fom.e countries 

 are more fubjed to thefe terrible convulfions than 

 others. Though this fubjed has been treated of by 

 ieveral authors, I think it my duty here to deliver 

 the opinion v^hlch to me feems moft probable. 



Experience has fufficiently fhewed, efpecially in 

 this country by the many vokan^oes in the Cordil- 

 leras which pafs through it, that the burfting of a 

 new burning mountain caufes a violent earthquake, 

 fo as totally to deflroy all the tov/ns within its 

 reach; as happened at rPie opening of the volcano in 

 the defart of Carguagoazo as mentioned in Vol. f. 

 This tremulous motion, which we may properly 

 call an earthquake, does nor fo ufualiy happen in 

 cafe of a fecond eruption, when an apperture has 

 been befoi^e made j or, an lead, the motion it caufes 



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