121 



in the department of Orne, lasting for five or six 

 minutes : this was heard for a distance of 75 miles 

 round. 



2. Some moments before the explosion at l'Aigle, a fire- 



ball in quick motion was seen from several of the 

 adjoining towns, though not from l'Aigle itself. 



3. The explosion was due to the bursting of the fire-ball. 



4. There was absolutely no doubt that on this day many 



stones fell in the neighbourhood of l'Aigle (153 T). 

 Biot estimated the number of the stones at two or three 

 thousand: they fell within an ellipse of which the larger axis 

 was 6*2 miles, and the smaller 2*5 miles, and this inequality 

 would indicate not a single explosion but a series of them. 

 With the exception of a few little clouds of ordinary character, 

 the sky was quite clear. 



The exhaustive report of Biot, and the conclusive nature 

 of his proofs, compelled the whole of the scientific world to 

 recognize the fall of stones on the earth from outer space as 

 an undoubted fact. 



Since that date many falls have been observed, and the 

 attendant phenomena carefully investigated. These observa- 

 tions teach us that meteorites, as they are now called, fall at 

 all times of the day and night, and at all seasons of the year, 

 while they favour no particular latitudes : also they are found 

 to be quite independent of the weather, and in many cases 

 have fallen when the sky has been perfectly clear : even 

 where stones have fallen in what has been called a thunder- 

 storm, we may reasonably suppose that the luminous pheno- 

 mena have been mistaken for lightning, and the noise of the 

 explosion for thunder. 



It is found that meteorites enter the atmosphere with 

 planetary velocities ranging from 10 to 45 miles per second. 

 Let us attempt to follow the course of such a body. 

 So long as the body is moving through ' empty space ' 

 the only heat it receives will be that sent direct from the sun; 

 the meteorite will thus be probably very cold, and, from its 

 size and want of luminosity, invisible to an observer on the 

 earth's surface. A very speedy change must take place. 

 Assuming the law of resistance of the air for a planetary 



