ON THE INTERACTION OF NATURAL FORCES. 179 



hot, the friction was long ago thought of which they 

 experience in passing through the air. We can now 

 calculate that a velocity of 3,000 feet a second, supposing 

 the whole of the friction to be expended in lieating 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 to tifty 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 sur- 

 faces. 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 processes which seem to have played an im- 

 portant 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 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 



