Ch.VII. south AMERICA. §9 



and fire exift only at the inftant when the matter be- 

 comes inflamed, and the air fpreading itfelf chroiigli 

 all the veins, the light is extinguifned by its dilata- 

 tion, and becomes afterwards imperceptible. It is 

 neceflary to fijppofe that there muil be fome, tho' a 

 fliort interval, between the inflamimation and efFe6l:. 

 Neither is the flamiC permanent, the fubflances ig- 

 nited not containing thofe folid and oleaginous par- 

 ticles which fupply the volcanoes. Eefides they are 

 not in fufficient quantity to afcend from the fubter- 

 raneous caverns where they took fire to the fuper- 

 ftcies of the earth. Farther, this not being the place 

 where the matter was originally contained, but that 

 where it has forced a pafilige for the quantity of 

 air which its rarefaction augmented, the firft light 

 is lofl: among the meanders of its courfe, and there* 

 fore not to be feen v/hen the wind violently forces 

 a paffage. There have, however, been inftances 

 when the light has been feen, though much oftener 

 the fmioke ; but this is generally loft in the clouds of 

 duft afcending at the time of the concuffion. 



The (hocks are repeated at intervals, of a few 

 days, fomctimes of a few hours; proceeding from 

 the matter being difperfed in different places, and 

 each in a different degree of aptitude for inflam- 

 mation, one part kindling after another fucceffive- 

 iy, as each is more or lefs prepared. Hence pro- 

 ceed alfo the different violence of the fhocks and the 

 different intervals of time. For the quantity firfl: in- 

 flamed increafes, by its heat, other inflammable por- 

 tions of matter ; whence a part which v^ould not have 

 been ignited till after fome days, by means of this ad- 

 ventitious fire, becomes fo within a few hours. The 

 Tecond fhocks are more violent, and caufe a greater 

 deftrudion than the firfc, for the fire of the portion 

 of matter which is firfl: inflamed, though in itielf 

 'fmall, is fufficient to accelerate the ferrnentation of 

 2 a much 



1 



