ASTRONOMICAL PROGKKSS IX 1896. 



51 



each one 16 centimetres in size and covering four 

 square degrees i-f space, will have been used. To 

 ratal"gui- this celestial host by visual means would, 

 \\vre it a possibility, have required thousand- f 

 years : but could all the plates have been simul- 

 taneously exposed, one hour would have served in 

 depicture Them all. An average first-magnitude 

 star will give an image on the modern sensitive 

 plate in one five thousandth of a second: a sixth- 

 magnitude, the smallest visible to the unaided eye, 

 in one second : but a star of the fourteenth magni- 

 tude requires an hour for its registration. 



Unfavorable weather, imperfect plates, and faulty 

 impressions all have conspired to delay the final 

 work on both the astrographic catalogues and charts. 

 At the dreenwich Observatory, during the past year 

 the astrographic equatorial has been devoted to the 

 taking of catalogue plates, and it is gratifying to 

 :'d that during this period forty negatives, with 

 ' stars, have been measured by Miss Turner, 

 who is assigned to this important and delicate work. 



As this century nears its close, we rejoice that it 

 has this valuable legacy to bequeath to its successor, 

 rendered possible in this age only by the penetra- 

 tive power of the photographic eye, whose ken so far 

 exceeds the possibilities of our greatest telescopes. 



A New Ring: Nebula. Annular nebula? are the 

 rarest of the various classes into which they have 

 been divided. Until recently only six were known, 

 and but one of these is at all conspicuous, viz., the 

 ring nebula of Lyra, and it is therefore a pleasure 

 to record the discovery of another by Walter F. 

 Gale, of Australia, on June 4, 1894, but only lately 

 announced to the world. Of it he says: "While 

 i'ing in the constellation Grus with the Si-inch 

 reflector at IPaddington. New South Wales, I ob- 

 served a faint elliptical nebula not down in 

 Dreyer's New General Catalogue, which I there- 

 fore suspected to be a comet. No motion was 

 detected on the following night, and it proved a 

 nebula not of the ordinary kind, but a nebulous 

 ring with the interior filled with very much fainter 

 matter, like the celebrated one in Lyra." He made 

 its approximate position as 21 h 52 - l m ; declination 

 south 39' .V.i . 



Dr. Swift, of Lowe Observatory. Echo Mountain. 

 California, has examined this object and confirms 

 the description given by its discoverer, and pro- 

 nounces it second only to that of Lyra, which it 

 resembles. 



Astrophysical Standards. At their first an- 

 nual meeting in New York. November, 1894. the 

 editorial staff of the "Astrophysical Journal." Profs. 

 Young. Pickering. Rowland. Michaelson. Hastings, 

 Keeler, and Hale being present, it was resolved 

 almost unanimously that the following rules be 

 adopted : 



" 1. That the Rowland scale of wave lengths be 

 chosen. 



"2. That the 10- 10 metre or 10- 1 millimetre be 

 adopted as the unit of wave length. 



" :>. That the kilometre be the unit of motion in 

 the line of sight. 



" 4. That the hydrogen lines be designated Ha, 

 H/3. ll-y, 118, etc., beginning at the red end of the 

 spectrum. 



" 5. That the maps of the spectra be printed with 

 the red end on the right. 



" 6. That tables of wave lengths have the shortest 

 placed at the top." 



To those members unable to be present at this 

 convention full reports were sent and voting ballots 

 containing the six propositions. The absentees 

 were Profs. Cornu. Duner, Huggins. Tachini. Vogel. 

 . Ames. Campbell. Crew. Frost, and Wadsworth. All 

 save Vogel voted for proposition 2, he preferring 

 the millionth of a millimetre. 



The Great Spanish Aerolite. This meteor, 

 which exploded over the city of Madrid on Feb. 10, 

 IMHi. is probably the largest that has fallen during 

 historic times in any civilized country, and r 

 anew the question of origin. From calculations 

 based on comparison of various observations from 

 many points it could have been but 14 or 15 miles 

 above the town at the instant of explosion. Its 

 tremors and reports extended over a radius exceed- 

 ing 50 miles. The detonations were tremendous, 

 as if thousands of tons of modern explosives had 

 gone off at that height. As the atmosphere at that 

 level is exceedingly rare, its force must have been 

 tremendous to shake the Earth over so large an area. 

 It came in daylight, but its brilliancy surpassed that 

 of the sunshine. It was seen at Gibraltar and heard 

 at places far from the point of explosion. 



The Next Great Meteoric Shower. The great 

 Leonid star shower of the years 1799, 1833, and 1866 

 will doubtless repeat itself in 1899 on the morning 

 of Nov. 15. Then the Earth will again pass through 

 the center of the swarm of meteoroids, as they are 

 called before combustion. As this aggregation is 

 immense in length, one end will encounter the 

 Earth in 1898 and the other in 1900, making con- 

 siderable showers in those years also. And as there 

 are many meteoroids considerably in advance of the 

 main cluster, forerunners of the great shower will 



Srobably come within the Earth's atmosphere on 

 ov. 14. 1897. so that it is not too early to call at- 

 tention to the expected phenomena. The thickness 

 of this meteoroidal stream is about 100,000 miles, 

 and the duration of the shower is equal to the time 

 of diagonal passage of the Earth through it, usually 

 from midnight to dawn. This, the most wonderful 

 of all the star showers, may be traced back to A. D. 

 126. when the meteor cornet (Tempel's) was captured 

 by Uranus, as calculated by Leverrier. 



As there is a light shower of Leonids every No- 

 vember, we know that there is a vast ring formed 

 by the comet's tail, and that the immense shoal in 

 one portion is the product of the exploded comet 

 itself, through which we pass once every thirty- 

 three years and a day, as the following shows : In 

 1799 the great shower occurred on Nov. 12 : in 1833 

 on the 13th ; in 1866 on the 14th ; and it is there- 

 fore looked for in 1899 on the morning of the loth. 

 The meteoroids that compose this stream make a 

 revolution around the Sun in about thirty-three and 

 a quarteryears.and.by consequence, the Earth passes 

 through it in a new place each year. At aphelion 

 the ring crosses the orbit of Uranus, and at peri- 

 helion that of the Earth. The inclination of the 

 plane of its orbit to the ecliptic being 16 C 46'. it can 

 not intersect the orbits of Saturn. Jupiter, and 

 Mars. The length of the swarm is so enormous 

 that, although at perihelion it moves at the rate of 

 nearly 25 miles a second, yet it takes it two years to 

 pass the Earth, so that when its hinder part is still 

 with us its advancing side will have reached the 

 orbits of Jupiter and Saturn. Notwithstanding 

 this extent, it is but a fraction of the entire orbit. 

 This great cluster will reach the Earth's orbit about 

 June 1, 1899, but the Earth will not have anived 

 there then, but will be due nearly six months later, 

 when our planet will plunge into the swarming 

 mass, and for at least five hours we shall experi- 

 ence a literal rain of fire. 



These meteoroids are dark bodies, and it is only 

 when they pass into our atmosphere and are ignited 

 by friction with it that they become visible for one 

 or two seconds. In whatever part of the sky they 

 may appear, their paths may be traced backward to 

 the radiant, now and for years to come, near the 

 sickle of Leo. 



Yerkes Observatory. This mammoth observa- 

 tory, just completed, was founded in 1892 by Charles 



