Section III., 1896. [ 91 ] Trans. R. S. C. 



VII. — The Distribution of Aerolites in Space. 



By Arthur Harvey. 



(Read May 20, 1896.) 



The periodicity of swarms of shooting stars is now generally admitted. 

 The great fall of the 11th and 12th November, 1799, was described by 

 Humboldt and Bonpland, who were in South America and found that a 

 similar display had been seen on the same days, thirty-three years before. 

 In 1831, 1832 and 1833, at the same period of the year, there was an 

 abvmdance of these meteors, and Arago was induced to write, in 1835, that 

 '"there exists a zone composed of millions of small bodies whose orbit cuts 

 " the plane of the ecliptic at about the point which our earth annually 

 " occupies between the 11th and 13th of November. A new planetary -world 

 " is beginning to be revealed." Olbers investigated the subject and found 

 the period of revolution of these meteorites to be a little over thirty-three 

 years, while the most numerous aggregation in the orbit was that through 

 which the earth had passed in 1766, 1799 and 1832, and he predicted a f 

 fine display for 1866. A brilliant shower was noted on the 13th and 14th 

 November of that year, especially in England, and we may reasonably 

 expect another in 1899. We see some of this swarm every year, but its 

 orbit is not packed with equal thickness in all parts, and the numbers 

 therefore vary. Necessarily, however, they seem to come from the same 

 radiant point in the heavens, and as this is near y Leonis, they are called 

 Leonids. Many other swarms are now recognized as periodical, each 

 having its separate radiant and its special days, each as the Geminids 

 from 6-12 December, the Lyrids from 20-26 April, the Perseids about the 

 10th of August. 



It was perceived about thirty years ago that the orbit of the Leonids 

 is closely related to that of Tempel's comet, seen in 1866. A swarm on 

 November 27th has the same elements as Biela's comet. The Perseids' 

 orbit agrees with that of the bright comet 1862 III. The new astronomy 

 therefore holds that there is an intimate connection between comets and 

 shooting stars, and it is thought that through some repulsive action, 

 which is most violent near perihelion, the loosely aggregated materials of 

 comets get scattered into a long trail, if not into a complete ring. The 

 incandescence of these materials, by friction in our atmosphere, when the 

 earth in its revolution swoops through their path, is thought to give rise 

 to the ijhenomenon of shooting stars. 



Professor Newton, of Yale, calculates at seven and a half millions the 

 number that daily fall, and the same astronomer has made another in- 



