476 



NATURE 



[September 15, 1892 



OUR ASTRONOMICAL COLUMN. 



Discovery of a New Satellite to Jupiter.— A telegram 

 from New York announces that Prof. Barnard, of the Lick 

 Observatory, Mount Hamilton, California, has discovered a 

 fifth satellite to Jupiter. It is of the thirteenth magnitude, 

 with a period of revolution round the primary of I7h. 36m., its 

 distance from the centre of the planet being 112,400 miles. 



Variation of Latitude.— Dr. Chandler, in the Astrono- 

 mical Journal No. 273, concludes his series of very important 

 articles on the discussion of observations with regard to the 

 cause of the variation of latitude. The material he has used 

 comprises more than thirty-three thousand observations, made 

 in seventeen observatories with twenty-one different instruments, 

 a.s many as nine distinct methods of observation having been 

 employed. Out of the forty-five series in which these observa- 

 tions are arranged, only three show results which do not har- 

 monize with the general law as stated in the fifth article (see 

 "Astronomical Notes," Nature, vol. xlvi. p. 211). The 

 values of the three come out negative, and as they are numeri- 

 cally small, they can be with justice discarded, for, as Dr. 

 Chandler says, "a mere rejection of a single discordant equa- 

 tion (out of a total number of 427), in two cases, and of two in 

 the third, would convert them into positive values." Instead, 

 then, of the ratio of the difference of the two moments of inertia 

 to the principal one being I°'l8, and perfectly uniform as given 

 by theory, observation suggests the value o°'85 (for 1875), the 

 motion not being uniform but subject to a slow retardation 

 which "in its turn is not uniform." The first difference was 

 soon found by Prof. Newcomb to be due to a defect in the 

 theory, an allowance of the earth's elasticity not having been 

 taken sufficiently into account, but with regard to the second he 

 urges an objection "on the ground of dynamic impossibility." 

 In such a discussion as this of course an outside opinion cannot 

 be counted of much value, but we quite agree with Dr. Chandler 

 that if an observed fact disagrees with the result of theory, and 

 a flaw is found in the theory, there can be no reason why 

 another observed fact of equal weight, but also in discord with 

 theory, should be regarded as "impossible." 



Bright Streaks on the Full Moon. — In Asironomische 

 Nachrichten, No. 31 11, Prof. Pickering gives a brief condensed 

 account of the investigation that has been carried out at Are- 

 quipa with regai-d to the systems of bright streaks, especially 

 round prominent craters, that are visible on our satellite at the 

 period of the second and third quarters. The instrument em- 

 ployed was the 13-inch, and the magnification ranged from 450 

 to ii2odiam.eters. The chief results noted were: — (l) That 

 the streaks of the systems round many of the large craters are 

 pot oriented to the centre of the prime crater, but towards other 

 craters whose dimensions are considerably smaller. (2) These 

 minute craters are extremely brilliant, and rarely exceed one 

 mile in diameter. (3) Some streaks are found to lie across or 

 upon ridges ; these are very seldom connected with small craters. 

 (4) In the case of Copernicus, streaks are found to start from 

 craterlets inside the rim and low up the inner side of the walls, 

 and down the other side. The rim of Tycho also contains simi- 

 lar craterlets, but the streaks do not extend very far. (5) A 

 difference in colour was noticed between the streaks systems of 

 Copernicus, Kepler, and Aristarchus, and those of Tycho, the 

 last-mentioned being considered whiter than the others. (6) 

 There are no very long streaks ; their general length may be 

 reckoned from ten to fifty miles. What have been previously 

 taken for long streaks are found, by .minute observation, 

 to be simply a series of these smaller ones connecting 

 up, apparently, many small craters. That extending from 

 the regions of Tycho across the Mare Serenitatis is so 

 constructed. In seeking an explanation to account for the 

 origin of these bright streaks. Prof. Pickering suggests that if, for 

 example, the craterlets on the rim of Tycho were constantly 

 emitting large quantities of gas or steam, which in other regions 

 was being absorbed, " we should have a wind uniformly blowing 

 away from that summit in all directions." Should other crater- 

 lets in the vicinity "give out gases mixed with any fine white 

 powder, such as pumice, this powder would be carried away 

 from Tycho, forming streaks." This hypothesis, besides ex- 

 plaining the presence of the streaks themselves, satisfies . very 

 well the fact that they can only be seen after and before the first 

 and last quarter of the moon phase, for it is only at this time 

 that the contrast would be best seen. 



Nova AuRiOiE.— Onthe receipt of Mr. H. Corder's infor- 

 mation relative to the brightening of Nova Aurigse, Mr, Espin 

 made an examination of its light on August 21, and found that 

 the star was of the 9*2 magnitude. Since then Prof. Kiistner, 

 has also observed it (August 31, 11 m. '4 Bonn meantime), and 

 reckoned it to be as bright as on March 21 last. The Astro- 

 nomer Royal's photographic determination, made on August 

 30, accounts it to be about the 12th magnitude. 



New Observatories. — Mount Monnier, in the Maritime 

 Alps, has been visited by M. Bischoffsheim and M. Perrotin, 

 with the object of setting up a new observatory. It is proposed 

 to raise on the summit (2800 metres altitude) an observatory, 

 the work of which will be commenced next April. V Astronomie 

 for September also informs us that the Astronomical Observatory 

 of Abbas- Touman (lat. N. 41° 46', long, E. Paris, 40° 32') 

 will be ready for work in a few weeks. The observatory is 

 already installed with a refractor of 29 inches, and as it is 

 situated at a considerable height, it will be used for those special 

 stellar studies which are difficult at Pulkowa, Moscow, and 

 Kazan. 



Solar Observations at Rome.— Prof Tacchini, in the 

 July number of Memorie della Societd. degli Spetlroscopisti 

 Italiani, gives in tabulated form the results of the observations 

 made at the Royal College with reference to the prominences 

 seen at the sun's limb during the months of April, May, and 

 June. In the table showing the frequency of these phenomena 

 for every xo° of latitude north and south, we find that the num- 

 bers for the three months respectively were 83, 97, and 147 for 

 the north, and 75, no, and 183 for the south latitude;. This 

 shows an excess of 41 for the south, the zone in which they 

 mostly occurred being ( - 50° - 60°) : the zone of greatest 

 frequency for the north was ( -)- 60° + 70°). The frequency at the 

 equator was comparatively small, 26 and 23 being the numbers 

 recorded for the zone of 10° each side. 



GEOGRAPHICAL NOTES. 



A Reuter telegram from St. John's, dated September ir, 

 says that the steamer Kite, which left that port three months 

 ago to relieve the Peary Expedition, has just arrived there, after 

 having successfully accomplished its object. Lieutenant Peary, 

 who is an engineer in the United States Navy, left America 

 early last year in command of a small expedition consisting of 

 only five men, the object of which was to sp;nd one or more 

 winters in Greenland for the purpose of scientific observation, 

 and to make an attempt to reach the North Pole across the 

 interior of Greenland. The commander of the expedition was 

 accompanied in this arduous enterprise by his young wife. The 

 winter quarters of the party were fixed at McCormick Bay, 

 whence Lieutenant Peary travelled 1300 miles northwards over 

 the inland ice, which he found to be in a favourable condition 

 for his journey. After making some important discoveries, the 

 explorer returned to the quarters at McCormick's Bay, where, 

 according to previous arrangements, he awaited the arrival of 

 the relief expedition. Lieutenant Peary, his wife, and his five 

 men are all well. Lieutenant Peary's great sledge journey com- 

 menced on May 15 last on the true ice cap of Greenland at the 

 head of McCormick's Bay, and at an elevation of four thousand 

 feet. The explorer, who took with him only one man and four- 

 teen dogs to draw the sledge, passed along the edge of the 

 Humboldt Glacier and then across the feeder basins of the St. 

 George's and Osborne Glacier system. On June 26 he reached 

 the 82nd parallel. Here the coast trended to the north-east, 

 and then east, and finally compelled the explorer to pursue a 

 south-easterly course. After four days' march, during which 

 the coast still stretched south-east and east. Lieutenant Peary 

 reached the head of a great bay in latitude 81° 37', and longi- 

 tude 34°. This was on July 4, and in honour of the day he 

 named this opening Independence Bay. The glacier terminating 

 on its shores he called the Academy Glacier. The land here 

 was of a red-brown colour and free from snow, and flowers, 

 insects, and musk oxen were abundant ; while hares, foxes, and 

 ptarmigan were also seen. On July 9 Lieutenant Peary and 

 his companion started on their return journey, taking a more 

 inland course, and in seven days' time they were travelling over 

 soft snow on the interior plateau, at an elevation of 8000 feet. 



NO. I 194, VOL. 46] 



