504 



NATURE 



\yan. 28, 1886 



If after an interval of three or four hours, when the stars liaye 

 equal zenith distances (and therefore are relatively but little dis 

 placed by refraction), the observation be repeated, the compari- 

 son of the two measures gives the means of determining the 

 amount of refraction with great accuracy. For the success of 

 the method it is, of course, essential that the measured distance 

 should be absolutely independent of every possible displacement 

 of the various parts of the apparatus in the interval between the 

 observations. This result is attained, M. Lcewy considers, by 

 placing the double mirror in such a position that the planes of 

 reflection for the two stars coincide, as he finds that under these 

 circumstances, whatever small displacements the prism may 

 undergo, the distance in the field of the telescope measured in 

 the plane of reflection or the projection of this distance on the 

 trace of the plane of reflection in the field remains invariable. 



ASTRONOMICAL PHENOMENA FOR THE 

 WEEK 1SS6 JANUARY 2,1— FEBRUARY 6 



(For the reckoning of time the civil day, commencing at 

 Greenwich mean midnight, counting the hours on to 24, is here 

 employed.) 



Al Greenwich on January 31 

 Sun rises, 7h. 42m. ; souths, I2h. 13m. 42'5s. ; sets, i6h. 46m. ; 

 decl. on meridian, 17° 19' S. : Sidereal Time at Sunset, 

 ih. 29m. 

 Moon (New on February 4) rises, 4h. S4m. ; souths, 9h. 21m. ; 

 sets, I3h. 47m, ; decl. on meridian, 18° 25' S. 



Planet 



Souths 



Sets 



Decl. on r 



3 ... 5 I III. occ. reap. 

 The Phenomena of Jupiter's Satellitt 

 Feb. h. 



Venus at least distance from the Sun. 

 Varial>!e-Sta}-s 



GEOGRAPHICAL NOTES 

 The Izrestia (1885, v.) contain another letter from M. 

 Potanin, describing his interesting journey to the Upper Hoang- 

 ho. Leaving Si-nin (Tsin-ning) on May 2, the E.xpedition visited 

 the Humbum Monastery — a trading-place for Russian goods 

 lirouglit from Urga and transported further to Thibet — and 



crossed a high ridge of mountains, the pass having an altitude 

 of no less than 12,000 feet above the sea. Following the valley 

 of the Lan-chou (Dun-ho-tsian on Prjevalsky's map), they 

 ascended to tlie plateau of Rchandza-tan, about 10,000 feet 

 above the sea, leaving to the north the snow-clad mountains of 

 Naryn-jamba, where Prjevalsky spent the winter of 1880. Only 

 Tanguts inhabit this elevated table-land, and a few lamas who 

 c-.cupy several monasteries. Descending from the plateau into a 

 deepvalley, Naryn-jamba, which joins thatof the Urung-vu River, 

 they were soon compelled to climb anotlier plateau of the same 

 height, the Ganja-tan, also peopled by Tanguts. The Amni- 

 Tunglyng Mountains raise their snow-covered summits towards 

 the north. On May 16 the Expedition reached the Labran 

 Monastery, situated at an altitude of io,ooo feet, and still con- 

 taining several hundred well-built houses, some of them with 

 two and three stories. The Gue-guen — a religious chief, who 

 is also chief of the neighbouring Tanguts — resides at this rich 

 monastery. From Labran, IVIM. Potanin and Skassi again 

 climbed a high plateau, and followed it until they arrived at the 

 Renu-kil^a Pass. A high snow-covered ridge extending west 

 and east on the left bank of the Tao-ho, was seen to the north ; 

 it is inhabited by a tribe of Tangut robbers — the Tebu. The 

 Tao-ho flows along a valley more than half a mile wide, between 

 picturesque craggy mountains, the slopes of which are thickly 

 wooded. The town Ming-cheu, situated in the same valley, 

 could thus soon be reached. Leaving it on June 16, the Expe- 

 dition easily reached also the Yalisan Mountain, which is the 

 watershed between the tributaries of the Tao-ho and the Yang- 

 tse-kiang, the ascent to the watershed offering no difficulties. 

 The further journey to Si-gu-sian was made in an alpine country, 

 intersected by deep and narrow valleys, which have a flora 

 offering some notable differences from that of the Si-nin and 

 Min-cheu region. The town Si-gu-sian is situated in the region 

 of the monsoons. The further intentions of the Expedition were 

 logo to Niang-pin, leaving M. Berezowski at Si-gu-sian to make 

 collections of mammals and birds. 



An extraordinary meeting of the Geographical Society of 

 Paris was held on the 21st inst. to receive M. de Brazza on his 

 return from his latest expedition to that part of Western Africa 

 which is now described as the French Congo. M. de Brazza 

 gave an account of his journey undertaken in the summer of 

 1883, on a subsidy from the Government of 1,250,000 francs 

 (50,000/.). In the beginning of June he and his party had 

 reached Franceville on the Ogowai. At this place he concluded 

 new treaties with the chiefs of the tracts adjoining the river, and 

 opened warehouses for carrying on trade. After instructing in 

 their duties the Europeans who were to remain at Franceville, 

 M. de Brazza crossed the elevated tract which separates the 

 basins of Ogowai and Alima to join Dr. Ballay, who was con- 

 ducting negotiations with the Bapfourous, a tribe settled near 

 the junction of the Alima with the Congo. Dr. Ballay had a 

 steamer on the latter river, the first French vessel of the kind 

 which had penetrated so far into these regions. M. de Brazza 

 then narrated his adventures in the tw-o years and nine months 

 during wliich he was engaged in exploring the banks of the 

 Ogowai, the Alima, and the Congo, in laying the foundation of 

 eight stations. 



The Ca'ciitta Englishman states that Mr. Needham, of the 

 Assam Police, and Capt. Molesworth, of the Bengal Staff Corps, 

 who left Sadiya on December 12 for Riina, in Thibet, have re- 

 turned to Dibrugarh. They reached Rima, but were unable to 

 enter the place, owing to the hostility of the Thibetans. Having 

 followed the course of the Brahmaputra the whole way from 

 Sadiya to Rima, they are able to state authoritatively that the 

 river corresponding in size to the " Sanpo," as described by the 

 explorer "A. K.," falls into it ; and that the identity of the 

 " Sanpo " with the Dijong may be deemed to be finally settled. 



The Government of the Congo State has commissioned 

 several geographers to execute maps of the entire State. Lieut. 

 Massari is surveying the right bank of the Congo between the 

 Alima and Mobangi Rivers. The topographical party under 

 Lieut. Junghers has surveyed Banana completely, and is now 

 engaged, in two divisions, in surveying the districts between 

 Banana and Bjina, and between Bomaand Vivi. The Swedish 

 geographer Herr Hakanson has drawn a map of the district 

 between the village of Mvinda, above Vivi, and the Issanghali 

 Station. 



Advices received in Berlin contradict the statement of the 

 death of the German traveller, Dr. Biittner, who is now alleged 



