H. Helmholtz on the Interaction of Natural Forces. 207 



Thus has the falling of the meteoric stone, the minute remnant 

 of processes which seem to have played an important part in the 

 formation of the heavenly bodies, conducted us to the present 

 time, where we pass from the darkness of hypothetical views to 

 the brightness of knowledge. In what we have said, however, 

 all that is hypothetical is the assumption of Kant and Laplace, 

 that the masses of our system were once distributed as nebulse 

 in space. 



On account of the raritj of the case, we will still further re- 

 mark in what close coincidence the results of science here stand 

 with the earlier legends of the human family, and the forebod- 

 ings of poetic fancy. Tlie cosmogony of ancient nations gene- 

 rally commences with chaos and darkness. 



Neither is the Mosaic tradition yerj divergent, particularly 

 when we remember that that which Moses names heaven is dif- 

 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 unmistakable traces of its old fiery^ 

 fluid condition. The granite formations of her mountains exhibit 

 a structure, which can only be produced by the crystallization of 

 fused masses. Investigation still shows that the temperature in 

 mines and borings increases as Ave descend ; and if this increase 

 is uniform, at the depth of fifty miles a heat exists sufficient to 

 fuse all our minerals.^' Even now our volcanoes 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 comparison with that reaching the earth 

 from the sun, is exceedingly small, and incre;ises the temperature 

 of the surface only about g'^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 surfi^ce only through the instrumentality 

 of volcanic phenomena. These processes owe their power almost 

 wholly to the action of other heavenly bodies, particularly to the 

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

 to the attraction of the sun 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 irregu- 



* Tliia 13 nut probable. The greater density and consequent better conductivity 

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

 researches of Messrs. Hopkins and Fnirbairn, would throw the region of liquidity 

 deeper.— Ta. 



