TERRESTRIAL SPHERE. 



tinresolvable nebulae with their soft lustre, and 

 of the resolvable nebulee with their twilight 

 gleamings, bring them as close to us as we 

 may, it still remains more than probable, from 

 the knowledge we have of the velocity of light, 

 that the light of the remote celestial bodies 

 offers the oldest sensible evidence of the exist- 

 ence of matter. So rises reflecting man, from 

 his stance on simple premises, to solemn and 

 noble views of natural formations to the deep 

 fields of space, where flooded with everlasting 

 light— 



" Myriads of worlds spring up like the grass of night."(92) 



From the region of celestial formations, from 

 the children of Uranos, we now descend to the 

 narrower domain of terrestrial forces, to the 

 children of Gaea. A mysterious band surrounds 

 and binds together both classes of phenomena. 

 In the import of the old Titanian Mythus ("), 

 all the powers of the universal life, the whole 

 mighty order of nature, is connected with the 

 co-operation of the heavens and the earth. 

 And, indeed, if the terrestrial ball, like all the 

 other planets, belongs, in virtue of its origin, 

 to the central body, the sun, and to its atmo- 

 sphere, once parted into nebulous rings, an in- 

 tercourse is still kept up, by means of light and 

 radiant heat, with this neighbouring sun, as 

 with all the farther suns that sparkle in the 

 firmament. The diversity of the mass of these 

 influences must not restrain the physical as- 

 tronomer from referring in a natural picture to 

 the connection and the dominion of common 

 and similar forces. A small fraction of the 

 terrestrial heat belongs to that of the universal 

 space through which our planetary system pur- 

 sues its way, and which, the product of all the 

 light-radiant stars, is nearly of the mean tem- 

 perature of our icy circumpolar regions, accord- 

 ing to Fourier. But what it is that excites the 

 light of the sun more powerfully in the atmo- 

 sphere and upper strata of the earth — how, 

 producing heat, it gives rise to electrical and 

 magnetical currents — how it magically kindles 

 and beneficially feeds the flame of life in the 

 organic forms that people the earth — all this 

 will form the subject of our considerations by 

 and by. 



Whilst we here apply ourselves exclusively 

 to the telluric sphere of nature, then, we shall 

 first take a glance at the relative proportions 

 of the Solid and the Fluid, at the figure of the 

 earth, its mean density, and the partial distri- 

 bution of this density in the interior of the 

 planet ; at the contained heat, and the mag- 

 netic charge of the earth. These relations in 

 respect of space, and these forces inherent in 

 matter, lead to the reaction of the interior upon 

 the exterior of our earth ; they lead through 

 the special consideration of an universally dif- 

 fused natural force — sub-terrestrial heat — to 

 the not always merely dynamic phenomena of 

 earthquakes in circles of concussion of various 

 extent, to the outbreak of hot springs, and the 

 mightier operations of volcanic processes. The 

 crust of the earth shaken from below, now in 

 pulses, suddenly and violently, now smoothly 

 and continuously, and therefore scarcely per- 

 ceptibly, alters in the course of centuries the 

 relations in point of elevation between the Dry 

 and the surface-level of the Fluid ; nay, the 

 form of the bed of the ocean itself. There are, 

 G 



at the same time, either temporary cracks, or 

 more permanent openings formed, through 

 which the interior of the earth comes into re- 

 lationship with the atmosphere. Welling up 

 from unknown depths, molten masses flow in 

 narrow streams along the slopes of the mount- 

 ains, here precipitously, there slowly, gently, 

 until the fiery spring runs dry, and the lava, 

 emitting vapours, solidifies beneath a crust 

 which it has formed for itself New rocky 

 masses then arise before our eyes, whilst older 

 ones, already formed by Plutonic forces, suffer 

 change, rarely through immediate contact, more 

 frequently from their vicinity to heat-radiating 

 centres or masses. In situations where there 

 is no eruption, crystalline particles are still dis- 

 placed, and then combined into denser textures. 



The waters present us with formations of a 

 totally different nature : aggregations of the re- 

 mains of plants and animals ; earthy, creta- 

 ceous, and clayey deposits ; conglomerates of 

 finely pulverized mountain species, overlaid by 

 layers of siliceous-shelled infusoria, and bone- 

 containing drift, the resting place of the re- 

 mains of animals that peopled a former world. 

 All that we see engendered in such variety of 

 ways beneath our eyes, and arranged in layers, 

 all that we observe so variously cast down, 

 and bent, and raised again, under the influence 

 of opposing pressure and volcanic force, leads 

 the reflective observer, who yields himself to 

 the guidance of simple analogies, to the com- 

 parison of the Present with times that have 

 long gone by. Through combination of actual 

 phenomena, through ideal amplification in ref- 

 erence to the extent as well as to the mass of 

 the forces in operation, we reach at length the 

 long-desired, the dimly-imagined, but first, in 

 the course of the last century, firmly-founded 

 domain of geognosy. 



It has been acutely observed, that, " with all 

 our looking through powerful telescopes, we 

 actually know more of the interior of other 

 planets than of their exterior — the moon, per- 

 haps, excepted." They have been weighed, 

 and their volumes have been measured ; their 

 masses and their densities are known, in either 

 case — thanks to the progress of the astronomy 

 of observation and calculation — with still in- 

 creasing numerical certainty. Over their phys- 

 ical constitution there hangs a deep obscurity. 

 It is only in our own earth that immediate vi- 

 cinity brings us into contact with the various 

 elements of organic and inorganic creation. 

 Here the garner of matter, in its multifarious 

 diversity, in its endlessness of admixture and 

 modification and change, in the ever-varying 

 play of forces evoked, presents the spirit with 

 its proper food ; the joys of investigation, the 

 unbounded field of observation, which, cultiva- 

 ting and strengthening the faculty of thought, 

 gives to the intellectual sphere of man's exist- 

 ence a portion of its grandeur, of its sublimity. 

 The world of sensible phenomena reflects it- 

 self in the deeps of the ideal world : the abun- 

 dance of nature, the mass of things discernible, 

 passes gradually into the domain of knowledge 

 approved by reason. 



And here, again, I touch upon an advantage 

 to which I have already alluded several times 

 —the advantage of that knowledge which has 

 a home origin, and of which the possibility la 



