508 Prof. Helmholtz on the Interaction of Natural Forces. 



ferent from the blue dome above us, and is synonymous with 

 space, and that the unformed earth and the waters of the great 

 deep, which were afterwards divided into waters above the firm- 

 ament and waters below the firmament, resembled the chaotic 

 components of the world. 



Our earth bears still the unmistakeable traces of its old fiery 

 fluid condition. The granite formations of her mountains ex- 

 hibit a structure, which can only be produced by the crystal- 

 lization of fused masses. Investigation still shows that the 

 temperature in mines and borings increases as we descend; and 

 if this increase is uniform, at the depth of fifty miles a heat 

 exists sufiicient to fuse all our minerals*. Even now our vol- 

 canoes project from time to time mighty masses of fused rocks 

 from their interior, as a testimony of the heat which exists 

 there. But the cooled crust of the earth has already become 

 so thick, that, as may be shown by calculations of its conductive 

 power, the heat coming to the surface from within, in compa- 

 rison with that reaching the earth from the sun, is exceedingly 

 small, and increases the temperature of the surface only about 

 ^o^th of a degree Centigrade ; so that the remnant of the old 

 store of force which is enclosed as heat within the bowels of the 

 earth, has a sensible influence upon the processes at the earth's 

 surface only through the instrumentality of volcanic pheno- 

 mena. These processes owe their power almost wholly to the 

 action of other heavenly bodies, particularly to the light and 

 heat of the sun, and partly also, in the case of the tides, to the 

 attraction of the sim and moon. 



Most varied and numerous are the changes which we owe to 

 the light and heat of the sun. The sun heats our atmosphere irre- 

 gularly, the warm rarefied air ascends, while fresh cool air flows 

 from the sides to supply its place : in this way winds are generated. 

 This action is most powerful at the equator, the warm air of 

 which incessantly flows in the upper regions of the atmosphere 

 towards the poles; while just as persistently at the earth's sur- 

 face, the trade-wind carries new and cool air to the equator. 

 Without the heat of the sun, all winds must of necessity cease. 

 Similar currents are produced by the same cause in the waters 

 of the sea. Their power may be inferred from the influence which 

 in some cases they exert upon climate. By them the warm 

 water of the Antilles is carried to the British Isles, and confers 

 upon them a mild uniform warmth, and rich moisture ; while, 

 through similar causes, the floating ice of the North Pole is 



* This is not probable. Tbe greater density and consequent better con- 

 ductivity of the mass, and the elevation of the point of fusion by pressure, 

 established by the researches of Messrs. Hopkins and Fairbairn, would 

 throw the region of liquidity deeper. — Tr. 



