52 On tilt Iron Meteorite 



tembor 23d ; mid since the latter \vAYt of August it Lad been ob- 

 served by Secchi, still separated into two portions, but niiicb 

 smaller and at a distance of 500, OCO leagues. Since theii it has 

 never been seen : so that Biela's comet, broken in twain since 

 1846 to 1852, has been considered as lost. 



According to calculation, it should have been seen in 1859, 

 1866, 1872, 1879, and 1885 ; but though astronomers have eagei"- 

 ly scanned the heavens, it lias never again appeared. 



On K'ov. 27th, 1872, there occurred, over all Europe, a showei- 

 of meteoi'S such as never lief ore had happened ivithin the wevKrrif 

 of man ; and it is remarlcable to note that calculation slioivs the 

 orhit of Biela's cornet and that of this inniiinerahle host offalliiKj 

 stars to be the same. 



Befoi'e 1870, astionomers considered meteors as having a plane- 

 tary origin r.nd as forming rings around the sun, with nearly 

 circular oi- elliptical orbits and with velocities analogous to that 

 of the earth. 



In 1870, Pi'ofessor Schiaparelli, of Milan, surprised at the ve- 

 locity of these bodies, which presupposes a parabolic orbit, sus- 

 jiected that they might have, like comets, an origin foreign to 

 our system, and proposed the following theory : 



Let us suppose a nebulous mass, or one formed of any kind of 

 widely separated molecules, situated at the limit of the sphere 

 of attraction of our sun, and that being animated with a relative 

 motion, it begins to feel the solar influence. Its voliime being 

 very great, its points are situated at greatly varying distances. 

 From this it results, that when such bodies commence to fall 

 toward the sun, the unec{ually distant points gain unequal veloci- 

 ties. Notwithstanding these differences, calculation proves that, 

 the periheliac distances of the different molecules are soon modi- 

 lied, and the orbits are so nearly alike that the molecules will 

 follow each other, forming a species of chain, or current, which 

 will take some time to pass around the sun. A mass whose di- 

 ameter is equal to that of the sun, would take many centuries to 

 comj^lete this motion. This current represents ph3^sically and 

 visibly the orbit of meteoric bodies, in the same way that a stream 

 of water represents the parabolic trajectory of each molecule as 

 a separate projectile. If, in its course, the earth should encounter 

 such a procession of bodies, it would pass through them and many 



