July 26, 1883] 



NATURE 



309 



sure the density varies proportionally with the pressure within 

 certain limits, the true constant of refraction should be that 

 function of the index of refraction and of the density which is 

 independent of pressure. In point of fact Prof. Quincke's 

 experiments confirm the formula of Dale and Gladstone, since 



!i-l — = **' — , where s 1 is the density under any given 



s j l 



pressure, and / u 1 the observed refractive index under the same 

 pressure. To put the matter in simple phrase, the decimals of the 

 refractive index increase proportionately with the density. 



In a further paper in Wiedemann's Annalen, Prof. Quincke 

 has given some details concerning the experimental methods 

 pursued in his investigations, together with figures of the appa- 

 ratus and tables of results for a large number of liquids under 

 different conditions. 



M. Bleekrode has lately described in the yournal de Phy- 

 sique a very convenient form of apparatus for projecting galvanic 

 experiments on a screen. It consists of a glass bath (6 cm. long, 

 5 cm. high, I cm. broad), at either end of which is a metallic 

 support which not only makes contact with the two plates that 

 are immersed in the bath, but also are attached to a flat galvano- 

 meter which is placed on the top of the bath. The galvanometer 

 consists of a light ebonite framework the same size as the top of 

 the bath and 1 cm. thick, upon which is wound two or three 

 layers of insulated copper wire '3 mm. thick. A single needle 

 is used, supported on a pivot in the centre of the coil. The 

 whole apparatus is of such a size as to be easily used in any 

 lantern. 



In a recent number of Carl's Repertorium, Th. Edelmann 

 describes a very simple means of determining the specific weight 

 of a gas. His method consists in taking a column of gas which 

 presses on a membrane, then observing the displacement of the 

 membrane. This is a somewhat analogous action to the aneroid 

 barometer. The absolute arrangement being to have the mem- 

 brane strained on a metallic box about 30cm. diameter, this box 

 is in direct communication with a tube 2 m. long filled with gas. 

 Upon the membrane rests a light lever which carries a mirror at 

 its point of suspension ; thus by raising a scale at a considerable 

 di-tance the slightest movements can be observed and therefore 

 the density taken with the greatest accuracy. 



M, Mokin has lately brought out a new electric candle, one 

 great advantage in it being that the light may be extinguished or 

 relighted at any time. This is obtained by the attraction of a 

 piece of soft iron by a flattened solenoid ; fixed on the same axis 

 as the soft iron is a cam, upon whose position the proximity of 

 the carbon depends. This motion is easier and not so noisy as 

 the electromagnet as used by Wilde and others. 



M. Tommasi has brought out a new regulator in which he 

 uses selenium, whose resistance varies considerably with varia- 

 tions in the intensity of light. At present it has only been 

 adapted to regulating the position of the light of a Jablo 

 candle. 



THE latest ht out for making incandescent lamps is 



by Messrs. Boulton, Soward, and Probert. They electrolyse a 



carbonaceous gas between platinum electrodes, in a "lobe ; as 



1 an arch of carbon is formed the globe is exhausted and 



the lamp ready for use. 



srs. J. Elster AND H. Geitel have found that a 

 Zamboni pile can be made to work as an accumulator by charging 

 it from a Iloltz machine. After ten minutes they obtained a 

 spark with the poles 1 mm. apart. Peroxide of lead does not 

 work so well when i^ed ready formed. 



M. Reynier has published some figures concerning the work 

 done by a Led 1 nehe battery when used on a telephonic exchange. 

 Two ba'tenes of three cells each were used for thirty days of 

 seven hours' duration. The loss of weight of zinc during that 

 sime was 64'5 grnis., which represents 63, 235 coulombs. I his 

 is equal to a current of 0084 ampere during the month. Taking 

 the E.M.F. of a Leclanche cell at I volt, the total work done is 

 189,705 watts, which is equivalent to I h.p. every 52 minutes. 



GEOGRAPHICAL NOTES 



The new number (No. I of vol. iv.) of the German African 

 Society's Mittheiluncen gives a table of magnetic observations 

 and temperature made at different points of his route from 



Kakoma to Karema by Dr. E. Kaiser, who unhappily died last 

 November on the bank of the Rikwa lake. A copious list 

 follows of Dr. Kaiser's altitudes between Zanzibar and Kakoma. 

 On the basis of English maps of the Niger and the Binue, Dr. 

 Kiepert traces Herr Ed. Robert Flegel's route from Eggan to 

 Bida in September, 18S1, and thence by way of Keffi to Loko 

 in November and December of the same year. Summing up 

 Herr Flegel's topographies, Herr Stuck determines the latitude 

 of Loko at 7 58' 16" ± 7" N., and of Keffi at 8" 49' 22" ± 3" 

 N. In an interesting letter from Ngaundere amid the sources 

 of the Logone, dated August 22, 1SS2, Herr Flegel claims to 

 have discovered the source of the Binue, or at least an impor- 

 tant part of the territory from which this river takes its source. 

 On July 31 last Herr Flegel proceeded from Jola to the water- 

 shed between the tributaries of the Faro and the Binue, and on 

 August 17 reached the first fountain-brook of the Binue, passing 

 it and two further heads of the river on the 18th. Ascending a 

 steep mountain chain, the watershed between the Binue, Faro, 

 Logone, and Old Calabar system, he beheld the last stream, by 

 the inhabitants unanimously named the Binue in contradistinc- 

 tion to the Guzun-Binue (beginning of the Binue) he had first 

 passed. From the back of the mountains close by their encamp- 

 ment on the first rimclii (farm) of Ngaundere, the source of the 

 Binue was pointed out by the natives. If not the source, it was 

 undoubtedly one of the main sources. After a stay of four 

 months at Ngaundere Herr Flegel returned to Lokoja, whence, 

 in a letter of February 21 last, lie projects an early exploration 

 of the lands yet unknown to the south of the Benue and of the 

 watershed cro-sed by him the previous year. He also contem- 

 plates opening up the territories where the Tsad and the Niger 

 have their sources, and investigating the relations between these 

 two water-systems, examining Barth's hypothesis of a direct 

 water communication between the Tsad and the Niger by 

 means of the Mao Kebbi and the Jubori swamps. He 

 will further make inquiry into the political and ethno- 

 graphical relations between the Tsad and Niger territories. 

 Astron nnical topographies are given of places visited by 

 Lieut. Wissmann between Malange and Kiinbundu. There 

 are two interesting and instructive reports by Dr. Pogge and 

 Lieut. Wissmann on their expedition through the south-east of 

 the Congo basin, between Kimbundu and Nge Njangwe, from 

 July 31, 1SS1, to April 17, 1SS2. The Kioque, inhabiting the 

 country along the Luelle and the Chikapa, among whom the 

 two travellers journeyed for a month and a half, are described 

 as an intelligent and enterprising people, expert smiths, hunters, 

 and far-travelling merchants. Carrying on a large trade in gum, 

 and soon exhausting a district of its gum produce by their incon- 

 siderate method of going to work, they are in a state of perpetual 

 movement towards the north. Almost all the ivory which 

 reaches Loanda is forwarded thither by the Kioque from the 

 Tuschilange country. The Tuschilange (sing. Kaschilange) or 

 Baschilange (sing. Muschalange) are a mixed people, composed 

 of the aborigines and the Baluba, who have entered the country 

 from the south. Of the three divisions of them the central is the 

 Beua Riamba, i.e. sons of wild hemp, so called from their ex- 

 cessive addiction to smoking that herb, which is smoked more or 

 less in almost the whole of Africa, and produces an intoxicating 

 effect combined with coughing. The Bena Rieniba are forbidden 

 to keep goats or swine, and the travellers during their stay 

 among them suffered from the want of animal food. Crossing 

 the splendid river of Lubi, the travellers passed from the land of 

 the Baschilange to that of the Bassonge, who, according to Lieut. 

 Wissmann, occupy the highest industrial "position he had ever 

 seen negroes hold. Artistic working in iron and copper, weav- 

 ing, basket-making, carving, and pottery are all highly advanced 

 among them. Living in fair villages with large clean houses, 

 under the shade of palms and bananas, the men cultivate their 

 trim fields, and leave only the lighter work to their wives— a 

 relation in marked contrast to that existing among the peoples 

 they had hitherto visited. 



The July number of Hartleben's Rundschau fiir Geographic 

 und Statislik contains, among numerous others, the following 

 original papers : — Researches concerning Madagascar, by J. 

 Audebert. — On the Bedouins of Palestine, by R. Ranipen- 

 dahl. — On the three first German "Geographentage," by Dr. 

 Sigm. Giinther. — On the United States of Columbia ; these are 

 remarks accompanying a good map of the States in question. 



The commander of the Willem Barents, now on her fifth 

 North Polar expedition, has sent news to Amsterdam from 



