2S2 



VOLCANIC FIRE. 



serves, that there are trachytes, clinkstones, and basalts, of diffeFent 

 ages ; but in proportion as we advance towards the more recent vol- 

 canic formations, they appear isolated, superadded, and strangers to 

 the soil in which they are found. The lavas from existing volcanoes 

 vary at different periods of their eruptions ; we may, therefore, well 

 conceive, that the volcanic masses which, during thousands of years 

 have been progressively raised to the surface under very different cir- 

 cumstances of pressure and refrigeration, should present striking con- 

 trasts and analogies of structure and composition. 



OBSERVATIONS. 



From the various phenomena which volcanoes present, we may 

 with probability infer, that the internal part of our planet is either 

 wholly or partially in an igneous state, however difficult it may be to 

 explain in what manner this heat is generated and confined. In eve- 

 ry department of nature, our enquiries are terminated by ultimate 

 facts, beyond which further research becomes vain. The constant 

 generation and emission of light from the surface of the sun is more 

 inexplicable and surprising, than the constant generation of heat in 

 the centre of our planet; but we cannot refuse our assent to the fact, 

 though it is far beyond the power of the human mind to conceive, by 

 what means the particles of light are propelled through space with 

 such astonishing velocity. We are too apt to measure natural opera- 

 tions by their coincidence with the received systems of philosophy, 

 and to make our own ignorance the standard of truth. Had all the 

 volcanoes in the world been dormant for the last two thousand years, 

 and were we acquainted with their existence only by the writings of 

 ancient historians, we should discredit the fact, and prove its impossi- 

 bility by an appeal to establish chemical principles; we should fur- 

 ther accompany the proof with a pathetic lamentation over the credu- 

 lity of former times. The descent of stones from the atmosphere was 

 denied during a longer period, though the fact is now established be- 

 yond all doubt. 



Admitting the existence of central fire in the earth, it is not diffi- 

 cult to conceive that there may be determinate causes, by which at 

 certain periods its intensity is increased or diminished. We know lit- 

 tle respecting the operation of electric or voltaic energy in the labor- 

 atory of nature, but, from the existence of electric light at the poles, 

 we may infer that electric currents are passing through the earth, and 

 are important agents in many subterranean phenomena. Perhaps the 

 diflerent beds of rock which environ the globe may act like a series of 

 plates in the voltaic pile, and produce effects commensurate with their 

 vast magnitude. Voltaic energy is capable of supporting the most in- 

 tense degree of heat without access to atmospheric air, or even in va- 

 cuo ; and this for an indefinite time. 



Whatever origin we ascribe to subterranean fire, it must be recol- 

 lected, that its action, when confined beneath the earth, is altogether 

 different from that of fire on the surface, which changes and decompo- 

 ses almost all substances exposed to its action. It is well known that 



