354 DOMAIN XII. VOLCANIC. 



volcano. It is an unextinguished forge, which 

 in proportion to the violence of the fire, to the 

 nature of the fossil matter on which it acts, and 

 of the elastic fluids which urge and set it in mo- 

 tion, produces, destroys, and re-produces various 

 forms. The usual and natural figure of the sum- 

 mit of a volcanic mountain, is that of an invert- 

 ed concave cone within, and one solid and erect 

 without ; and such a configuration, in countries 

 which are no longer in a state of conflagration, 

 is one of the most certain indications of the ex- 

 istence of an ancient volcano. This cone, how- 

 ever, is liable to very great changes ; according 

 to the greater or less fury of the volcano, and the 

 quantity and quality of the matters ejected. Its 

 internal part, from more than one cause, is ex- 

 posed to continual violence and change. The 

 prodigious cavities of the mountain make it 

 almost appear suspended in the air. It may 

 easily therefore give way, and fall in; especially 

 on the violent impulse of new matters, which en- 

 deavour to force a passage through the upper 

 part ; in consequence of which the inverted cone 

 may, according to circumstances, present the 

 appearance of an aperture, or whirlpool, or a 

 gulf. Should the liquid lava pass through the 

 aperture, and continue there some time, its 

 superficies by the contact of the eold air losing 



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