143 COSMOS 



flering electric and magnetic currents, and awaken and geni- 

 ally vivify the vital spark in organic structures on the earth's 

 surface, must be reserved for the subject of our future consi- 

 deration. 



As we purpose for the present to confine ourselves exclu- 

 sively within the telluric sphere of nature, it will be expe- 

 dient to cast a preliminary glance over the relations in space 

 of solids and fluids, the form of the Earth, its mean density, 

 and the partial distribution of this density in the interior 

 of our planet, its temperature and its electro -magnetic ten- 

 sion. From the consideration of these relations in space, 

 and of the forces inherent in matter, we shall pass to the 

 reaction of the interior on the exterior of our globe ; and 

 to the special consideration of a universally distributed natu- 

 ral power subterranean heat ; to the phenomena of earth- 

 quakes, exhibited in unequally expanded circles of commo- 

 tion which are not referable to the action of dynamic laws 

 alone ; to the springing forth of hot wells ; and lastly to the 

 more powerful actions of volcanic processes. The crust of 

 the earth, which may scarcely have been perceptibly elevated 

 by the sudden and repeated, or almost uninterrupted shocks 

 by which it has been moved from below, undergoes, never- 

 theless, great changes in the course of centuries in the rela- 

 tions of the elevation of solid portions, when compared with 

 the surface of the liquid parts, and even in the form of the 

 bottom of the sea. In this manner simultaneous temporary 

 or permanent fissures are opened, by which the interior of 

 the Earth is brought in contact with the external atmosphere. 

 Molten masses, rising from an unknown depth, flow in narrow 

 streams along the declivity of mountains, rushing impetuously 

 onwards, or moving slowly and gently, until the fiery source is 

 quenched in the midst of exhalations, and the lava becomes 

 encrusted, as it were, by the solidification of its outer surface. 

 New masses of rocks are thus formed before our eyes, whilst 

 the older ones are in their turn converted into other forms by 

 the greater or lesser agency of plutonic forces. Even where 

 no disruption takes place the crystalline molecules are dis- 

 placed, combining to form bodies of denser texture. The 

 water presents structures of a totally difFert.it nature, as, for 

 instance, concretions of animal and vegetable remains, of 

 e&rthy, calcareous or aluminous precipitates, agglomeration^ 



