EXrERIMEXTS RELATIVE TO METEORITES. 313 



of these masses on the earth. That these circunistunces are constantly and 

 idc'Utically reproduced, is extremely remarkable. The fall of meteorites is 

 always accompanied by an incandescence suiliciently vivid to give to nii^ht an 

 api)earance of day, and to be perfectly ])erceptible even at noon-day. In con- 

 setpience of this vivacity of their light, the arrival of ineteorites in our atmo- 

 sphere may be seen at very great distances ; the fall at Orgueil (Tarn-et-daronne.) 

 of the 14tli i\lay 1SG4, was observed as far otf as Gisors (Eure,) a distance of 

 more than 500 kilometers,* (310i miles.) 



The light in question is, moreover, of very transient duration. It is thought to 

 be produced at the moment when the asteroid enters our atmosphere, and there- 

 fore at a great height, which, in the case of Orgueil, for exajnjjle, has been 

 computed at 65 kilometers, (40 miles.) It is owing to this incandescence that the 

 trajectory of meteorites, -which is in general hut little inclined to the horizon, is 

 suscei)tibleof being observed. Atrajectory of this nature was particularly verified 

 for the bolide of (Jrgueil just cited: proceeding from the west towards the east, 

 this bolide was followed from Santander and other points of the coast of Spain 

 to the place of its fall. Tiie incandescence allows, moreover, of an appreciation 

 of the velocity of the bolides, a velocity which has nothing analogous on the 

 earth, and which can only be compared to that of the planets revolving in their 

 orbits. This single circumstance would suthce to prove the cosmic origin of 

 meteorites. The meteorite of Orgueil appeared to traverse about 20 kilometers 

 (12:} miles) i)er second ; while in other cases velocities have been observed which 

 could not be estimated at less than 30 kilometers, (18.V miles.) 



The appearance of the bolide is constantly accompanied by a trail of vapors, 

 which arc themselves not destitute of a certain etl'ulgence. No instance of the 

 fall of a meteorite has occurred without being preceded by an explosion and 

 sometimes by several explosions. The noise of the explosion has been compared 

 either to that of thunder or to that of cannon, according to the distance of the 

 observers. It makes itself heard over a vast extent of country ; sometimes at a 

 distance of more than 100 kilometers in circuit, as in the fall at Oi'geuil. If we 

 rcllect that it is produced in regions where the air, highly rarefied, lends itself 

 very imi)erfectly to the ])ropagation of sound, we shall readily be convinced that 

 its intensity must be such as to surpass all else that is known to ns. After the 

 explosion a whizzing sound is heard, owing to the rapid passage of detached 

 pieces in the air, which the Chinese compare to the noise made In" the wings of 

 ■wild giX'i^c, or to that of a cloth which is torn. It should be added that these 

 phenomena have been observed not only in wid(^ly distant regions of the globe, 

 but at all seasons, at all hours, aiul often when the sky is serene and cloudless and 

 the air calm. Tempests, water-sj)outs, therefore, have no agency here. 



To obviate an objection which naturally presents itself to the mind, in relation 

 to the velocity of these bodies, attention must be drawn to an essential distinction. 

 The enormous velocity proper to the luminous body or bolide whi(di is seen 

 cleaving the atmosphere contrasts with that, incomparably more feeble, which 

 the fragments possess at the moment of their arrival on the earth. The bolide 

 moves like a body launched with a great initial velocity; on the contrary the 

 fragments which reach us in the sequel of the explosion ajjpear, in general, to 

 possess only a velocity comi)arable to that which would correspond to their 

 descent, mtjderated, besides, by the resistance of the air. It is to be added that, 

 as lh(^ bolides move in all directions, their relative velocit}^ all else being e(puil, 

 must necessarily vary according to the coiu'se of the trajectory with regard to 

 th(^ direction of the earth's rotaticm and motion in its orbit. 



The stones of any one fall are more or less numerous, and are always burning 

 Lot on the surface at the moment of their arrival, without, however, having pre- 

 served their incandescence. At Orgueil stones fell upon GO points, comprised 



* A kilometre is C2 huiulredlhs of a mile. 



