54 



ASTRONOMICAL PROGRESS AND PHENOMENA. 



Spectra of the Planets. The spectra of all the 

 planets, from Mercury to Saturn, are very simi- 

 lar, the differences being, as a rule, too slight 

 for a basis for any opinion as to their physical 

 constitution or the precise nature of their at- 

 mospheres. But the latest researches of Hug- 

 gins and Vogel have shown that the spectrum 

 of Uranus is quite unlike that of the others, 

 and approaches more nearly to that of Nep- 

 tune. It contains six broad bands, one of them 

 being coincident with H/3, but the identity 

 of the others is doubtful. These observations 

 have shown the erroneousness of Secchi's 

 map of the spectrum of Uranus. Neptune 

 shows eight absorption bands. 



Red-Sky Glows. This beautiful and mysteri- 

 ous phenomenon, that so suddenly manifested 

 itself in the autumn of 1883, still continues. 

 During the months of October and November, 

 1886, it on several occasions almost equaled 

 the gorgeous displays of 1883-'84. It has, how- 

 ever, differed from those in the non-appearance 

 of the second and third glows, and the partial 

 absence of the counter-glow, which for a long 

 time were three of its distinguishing character- 

 istics. The writer refers to its renewal as seen 

 from western New York. One accompanying 

 feature during its early appearance was the 

 "noon-glow," or "Bishop's ring," which was 

 generally considered to have a connection with 

 the sunset and sunrise phenomena ; but this is 

 now doubted by many, for the reason that, for 

 the past eighteen months, not a vestige of it 

 has been observed. This, however, does not, 

 any more than does the absence of the second 

 and third glows, and of the counter-glow (the 

 glow opposite the sun), prove their disunion. 

 Various hypotheses having been advanced to 

 account for these unwonted solar appearances, 

 and as there was no agreement between astron- 

 omers and meteorologists regarding them, H. 

 H. Warner, of Rochester, N. Y., offered a 

 prize of $200 for the best three-thousand word 

 essay on the subject, which was the means of 

 calling out a large number of able papers from 

 all over the world. These essays were sub- 

 mitted to three judges two astronomers and 

 one meteorologist who awarded the prize to 

 Prof. K. I. Kiessling, of Hamburg, Germany. 

 Two hundred and fifty dollars and seven gold 

 medals were also given to other contestants. 

 Prof. Kiessling was able to produce in his labo- 

 ratory all the observed phenomena except the 

 counter-glow. The processes used are de- 

 scribed in his papers, which will be found en- 

 tire, with three of the others that drew cash 

 prizes, in vol. i of the " Publications of the War- 

 ner Observatory." Nearly all of the essayists 

 advanced the theory of atmospheric dust as the 

 primary cause, the volcanic eruption of Kraka- 

 toa being, by the majority, esteemed the source 

 of this abnormal amount of matter in the at- 

 mosphere. The principal objections to this 

 theory are the inadequate quantity of erupted 

 material, and the long persistence of its at- 

 mospheric retention. The first is plausible, 



but the latter is groundless, as the atmosphere 

 is never free from dust, which is the cause of the 

 ordinary warm and mellow sunsets, of which 

 phenomena of the red glows of the past three 

 years are but an intensification. There is no 

 alternative but to ascribe this dust to volcanic 

 origin; for, had the earth encountered a nebu- 

 lous body, fully half its circumference must, in 

 a few minutes, have been ingulfed. That the 

 dust is long retained, is an argument in its 

 favor. If its source were Krakatoa, then it 

 must have been ejected with a velocity far sur- 

 passing that of a rifle-bullet, and thrown to a 

 height of 50 or 75 miles, far above winds and 

 clouds, where perfect quiescence reigns eternal. 

 Just how dust reddens light is not quite clear ; 

 but if, as Prof. Kiessling has proved, there can 

 be no condensation of moisture in an atmos- 

 phere absolutely free of dust, it follows that the 

 fine dust-particle may gather to itself moisture 

 that perhaps plays an important part in the pro- 

 gramme. This experimenter succeeded in red- 

 dening light only when the dust-particles are 

 of exactly the same size. Apropos to the as- 

 sertion that dust, under certain conditions, will 

 redden light, and that without the incasement 

 of each particle in a film of moisture (for we 

 can not suppose that there can be moisture at 

 the height the dust is supposed to reach), M. 

 Janssen, of Meudon, France, has succeeded in 

 condensing carbonic-acid gas to the density of 

 water, and at each compression a cloud of dust 

 was formed which, when a ray of light was 

 passed through it, became of a blood-red color. 



Canals of Mars. The "Bulletin Astrono- 

 mique " of the Paris Observatory, for July, 

 1886, contains an interesting article by M. Per- 

 rotin on the observation of Martial canals dis- 

 covered by Schiaparelli with the 8|-inch re- 

 fractor at Milan Observatory, Italy, during the 

 close approach, in 1877, of Mars to the earth. 

 By the aid of the Henry equatorial of 15-inch 

 aperture, he was able not only to confirm Schia- 

 parelli's discoveries, which astronomers were 

 loath to believe, but also to recognize the ca- 

 nals, even those that the Italian astronomer 

 had declared were double. At the latter time, 

 however, the planet subtended an angle of only 

 14". He also observed great temporary changes, 

 and even obscurations of some of the numerous 

 markings which were due, no doubt, to the 

 movements of clouds. M. Perrotin's observa- 

 tions were also confirmed by Mr. Denning, of 

 England, and by observers at Nice. 



Jnpiter's White and Red Spots. The great red 

 spot, which for eight years has attracted atten- 

 tion from astronomers, still continues to be 

 faintly visible, and, though its size and shape 

 remain ahout the same, its brick-red color has 

 greatly faded. From its first discovery until 

 now, its contour has been an oval, whose ma- 

 jor axis was 30,000 miles in length, and its 

 minor, 8,300. It undoubtedly appeared some- 

 what suddenly in 1878, while the planet was 

 lost in the sun's rays, as, when first seen, it 

 was of a magnitude not subsequently much, if 



