1 82 



SCIENCE- G OSSIP. 



iu Pevseus at tlie above College on November 12th, 

 13th, 14th, and loth. They will be well illus- 

 trated and likely to be very helpful. The hour 

 of commencement, 6 p.m., is perhaps a trifle too 

 early. 



A Parhelion on Mock Su.v. — This pheno- 

 menon appears to have been seen for nearly ten 

 minutes at Cushenduu, Co. Antrim, about Septem- 

 ber 3rd. It is said to have been of a blood-red 

 colour. 



Encke's Comet, h 1901, will be near Anlares, a 

 Scorpii, at the beginning of November, according 

 to Herr Thonberg's ephemeris. 



New Variable in" Cvgxus. a little south- 

 west of W. Mr. Stanley Williams, of Hove, has 

 discovered a tenth magnitude star, whicli after 

 3 d. 2 h. decreases for 3 h. 30 m. to twelfth mag- 

 nitude ; after thus i-emaining for .50 m. it again 

 increases during 4 h. 10 m. to its normal magni- 

 tude. This is, of course, of similar type to Algol. 



Star Atlas. — The Society for Promoting 

 Christian Knowledge has published a third edi- 

 tion, revised and enlarged, of Klein's Star Atlas, 

 with a translation of the explanatory text by 

 Mr. Edmund McClure. This atlas is too well 

 known to amateur astronomers to require a very 

 extended notice, but we may mention that the 

 positions of the stars have been corrected to 1900. 

 The notation of nebulae comprises not only the 

 Herschel Catalogue, but also the New General 

 Catalogue. There are eighteen maps, some printed 

 in colour. The size of the book is 12^ inches by 

 9 inches, and its price is 10s. 



Nova Persei. 1901.— TheRev. WalterSidgreaves, 

 of the Stonyhurst College Observatory, has commu- 

 nicated some important notes on the spectrum of 

 this starto Gae AstroHomhclie Nacliru-hten. No. 3,741. 

 All the hydrogen lines are now relatively weak, 

 excepting the one apparently identical with He. 

 These lines were altogether the brightest ones in 

 the early days of the star's apparition, and are well 

 shown in the lohotograph reproduced on p. 323, 

 vol. vii., of Scien'CE-Go.ssip. Now. some of them 

 are barely traceable, whilst lines unnoticeable in 

 the older photograph are quite conspicuous. 

 Father Sidgreaves has kindly sent us beautiful 

 prints of the photographs taken on August 27th 

 and September 5th, but they are too delicate for 

 reproduction ; the contrast between them and that 

 of March 3rd is most noticeable. Three bright 

 bands at wave-lengths 43(j-4, 39(;-9, and 386'9 are 

 each crossed by four strong lines of the same 

 relative intensities and at the same intervals. The 

 line 436'4 is now very prominent, considerably 

 stronger than H-y, its near neighbour. Where 

 these two overlap there is a line brighter than the 

 sum of the two bands. On August 27th the 

 spectrum consisted of bright bands at wa\e-length 

 500-7, 495-8, Ha, 471-3, 4137-9. 464-0, 43«-3, H7, 

 H8 barely traceable. He '\ brighter than all the 

 other hydrogen lines together situate at wave- 

 length 396-9, and 386-9. "in the note on p. 124 of 

 Science-Gossip the line spoken of as F (H/3) was 

 probably the one at wave-length 4713 due to helium. 

 The star is now in splendid position for observa- 

 tion, and when it has been focussed with a tele- 

 scope of 3 inches over a prism, or diffraction 

 grating, will show it not as a line, but as having a 

 set of bright images of varying intensity, each 

 image occupying the place of a liright line. 



CHAPTERS FOR YOUNG ASTRONOMERS. 



By Frank 0. Desnbtt. 



iCoiifinued from page 60.) 



SATURN'S SYSTEM (continued). 



The rings thus nearly or entirely disappear at 

 intervals of about fifteen years, the last time having 

 been in October, 1891, when the ring was lost oven 

 with the 36-inch Lick telescope. Since that time 

 the northern side of the rings has been presented 

 towards us, and it -will be so until 1907, when the 

 southern side will become visible, and remain so 

 for another fifteen years. The rings, therefore, 

 disappear when Saturn reaches that part of its orbit 

 situate where the constellations Leo and Mrgo are 

 conterminate, and again just after it attains the 

 constellation Pisces. At each of these points the 

 ring seems to disappear twice ; once when the 

 plane of the rings passes through the Sun, and 

 again when the same plane passes through the 

 Earth. When the planet reaches the portions of 

 its orbit midway between these points, at the 

 eastern border of the Taurus, and between Ophiuchus 

 and Sagittarius, the rings are seen widely open, as 

 shown in the accompanying- drawing- by Mr. Scriven 

 Bolton, who used a 4^-inch achromatic. The ring- 

 was discovered by Cassini in 1675 to be double. 

 T he black line can sometimes be seen with a telescope 

 as small as 2^ inches in aperture, with a power 

 of 120. The outer ring is usually not so bright as the 

 inner, and is known as A. Telescopes above 4 inches 

 aperture will sometimes sho-w this ring divided 

 into two portions by what is known as Encke's 

 division. This division does not always preserve 

 the same position on the ring, and is frequently 

 more visible on one side of the planet than the 

 other. Glimpses have sometimes been obtained 

 of other divisions. The inner ring, " B." is much 

 the brighter, gradually fading inwards ; the process 

 is usually gradual, but is sometimes apparently in 

 steps, as in the accompanying drawing by M. E. 

 Antoniadi. More than this was not seen even with 

 the giant reflectors of the Herschels and Schroter, 

 until in 1828 a shading- was observed between the 

 edge of " B " and the planet at the Roman obser- 

 vatory ; but no particular notice was taken of it. 

 In 1838 Galle of Berlin, with a 9-6-inch achromatic, 

 saw, measured, and published the observations of 

 this shading. Notwithstanding, it was not until 

 November, 1850. that attention became attracted 

 to it, when it was independently discovered by 

 G. P. Bond at Harvard, and Dawes at Watering- 

 bury, near Maidstone. It was found to be a third 

 inner dusky ring, semitransparent. the limb of 

 the planet being traceable through it. This ring- 

 is properly known as " C," but is frequently called 

 the " crape veil.'' It is visible under favourable 

 conditions with any good telescope abo\-e 3j inches 

 aperture. It is probable that the Cassini division 

 of the ring is filled with the same material as " C," 

 because from time to time it is noticed to be not 

 black. If the planet travelled over a bright star 

 it would be interesting- to watch its appearance in 

 passing these divisions of the ring, and also its 

 visibility when covered by the " crape ^eil." 



This wonderful ring system, the only large flat 

 surface known, was at one time thought to be 

 solid, and even to support mountains, but this has 

 been quite disproved. It was found, by the spectro- 

 scopic obser\ations of the late J. E. Keeler, that 

 the outer edge of the ring- rotated more slowly than 



