76 Notice of Active and Extinct Volcanos. 



by the head of a pin, at one end of a long beam, is distinctly 

 perceived at the other, in consequence of a vibration of all 

 its parts. The movement of a carriage upon the pavements 

 shakes vast buildings, and is communicated through great 

 masses of matter, as in the deep quarries under Paris. M. 

 Gay Lussac enquires, therefore, whether it is astonishing, 

 that a violent commotion, in the bowels of the earth, should 

 cause it to tremble through a radius of many hundred leagues. 

 This philosopher concludes, that earthquakes are the result 

 of the communication of a commotion through the mass of 

 the earth, so independent of subterranean caverns, (which 

 some have supposed favorable to the propagation of the 

 sound and motion) that these effects will be propagated the 

 more extensively, the more homogeneous the materials of the 

 earth are. 



Our knowledge of elastic agents justifies us in concluding, 

 that steam and gases, in a word, aeriform agents, as the im- 

 mediate moving power, are the causes of volcanic eruptions, 

 and of earthquakes. When evolved rapidly and suddenly, — 

 that is, in very great quantities, in a given short time, and 

 endowed with great elastic power by heat, they have, with- 

 out doubt, sufficient energy to rend mountains, to raise 

 floods of fiery lava — -to project stones to great heights in 

 the atmosphere — to rock alpine ridges, on their founda- 

 tions, to heave the ocean into unwonted undulations — to 

 shake continents, and the solid globe itself, to its very centre. 

 The effects of gunpowder, of fulminating preparations, and 

 of imprisoned steam, when suddenly liberated, (now so fa- 

 familiar to mankind,) fully justify us in attributing to elastic 

 agents, all that we have done in this statement. 



This subject has been fully illustrated by Mr. Scrope, in 

 his Considerations on Volcanos, of which we gave an abstract 

 in Vol. 13, page 100, which renders it unnecessary to repeat 

 the arguments there urged. 



Most hot springs have their origin from volcanic action. — 

 Many that are not connected with active volcanic regions 

 arise from basaltic rocks, and their composition is observed 

 to be similar to that of the waters of volcanic districts, espe- 

 cially in their containing soda or the mineral alkali. It is possi- 

 ble that some hot springs — as, for instance, those of Bath and 

 Bristol, may be derived from the fermentation of pyrites, or 

 from other chemical agencies, generating heat, and that the 

 permanency of the temperature may arise from the great 



