NATURAL PHILOSOPHY. 133 



friction to be expended in heating the solid mass, would raise a piece of 

 meteoric iron 1,000 C. in temperature or, in other words, to a vivid red 

 heat. Now the average velocity of the meteors seems to be thirty or forty 

 times the above amount. To compensate this, however, the greater portion 

 of the heat is, doubtless, carried away by the condensed mass of air which 

 the meteor drives before it. It is known that bright meteors generally leave 

 a luminous trail behind them, which probably consists of severed portions of 

 the red-hot surfaces. Meteoric masses which fall to the earth often burst 

 with a violent explosion, which may be regarded as a result of the quick 

 heating. The newly-fallen pieces have been for the most part found hot, 

 but not red-hot, which is easily explainable by the circumstance, that during 

 the short time occupied by the meteor in passing through the atmosphere, 

 only a thin, superficial layer is heated to redness, while but a small quantity 

 of heat has been able to penetrate to the interior of the mass. For this reason 

 the red heat can speedily disappear. 



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

 cesses 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 nebula in 

 space. 



On account of the rarity of the case, we will still further remark, in what 

 close coincidence the results of science here stand with the earlier legends of 

 the human family, and the forebodings of poetic fancy. The cosmogony 

 of ancient nations generally commences with chaos and darkness. 



Neither is the Mosaic tradition very divergent, particularly when we re- 

 member that that which Moses names heaven is different from the blue 

 dome above us, and is synonymous Avith space, and that the unformed earth, 

 and the waters of the great deep, which were afterwards divided into waters 

 above the firmament, and waters below the firmament, resembled the chaotic 

 components of the world. 



Our earth bears still the unmistakable traces of its old fiery fluid con- 

 dition. 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 we de- 

 scend ; and if this increase is uniform, at the depth of fifty miles, a heat ex- 

 ists 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 



V 



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 compari- 

 son with that reaching the earth from the sun, is exceedingly small, and in- 



* This is not probable. The greater density and consequent better conductivity of 

 the mass, arc! 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. 



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