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Ch. XXXIII.l EXPANSIVE POWEE OF LIQUID GASES. 



22" 



condensed gas, have its temperature sliglitlj raised, it Avill 

 often burst : for a slio^lit increment of heat causes the 



r 



elasticity of the gas to increase in a very high ratio. If a 



become 



instantly aeriform, or, in the language of some writers, it 

 flashes into vapour, and in rushing out often bursts the 



vessel. We have only to suppose certain rocks, permeated by 

 these liquid gases (as porous strata are sometimes filled with 

 water), to have their temperature raised some hundred 

 degrees, and we obtain a power capable of lifting superin- 

 cumbent masses of almost any conceivable thickness ; while, 

 if the depth at which the gas is confined be great, there is 

 no reason to suppose that any other appearances would be 

 witnessed by the inhabitants at the surface than vibratory 

 movements and rents, since the gases, in making their way 

 through fissured rocks or soft yielding strata, may be cooled 

 and absorbed by water. For water has a strong affinity to 

 several of the gases, and will absorb large quantities, with a 

 very slight increase of volume. In such cases there may be 

 no outburst at the surface, nor any obvious indication of 



of 



tempe 



sprmgs 



'mented 



and their mineral proper- 

 ties altered, but no volcanic explosion may be witnessed. 

 Whether a permanent change of level may be expected to 



occur as a consequence 



'mpaniment of such 



gene- 



ration and heating of gases in the interior of the earth's 

 crust, will be considered in the sequel. 



The volcano of Cotopaxi has been known to throw out, to 



mass 



me 



how the most solid substances which oppose the upward 

 passage of the exploding gases may be reduced to small 

 fragments, or even to dust, such as we see hurled to the 



mile 



->! 



to 



f^ 



A^lthough the 



theory which assumes that water jDlays a principal part in 



im 



of volcanic vents to the ocean, it seems still to follow naturally 

 that the superficial outbursts of steam and lava will be most 



^ 



