Feb. 26, 1 8 So] 



NA TURE 



409 



as possible the position occupied by the plane of polarisation of 

 the sky with respect to the position of the sun, he designed an 

 instrument by means of which the traces of the plane containing 

 the line of sight and passing through the sun could be compared 

 with those of the plane of polarisation as observed in a Savart 

 polari cope. With this instrument it was soon found that, 

 contrary to what has always been hitherto supposed, these 

 planes do not coincide with one another, but that the angle 

 between them may even exceed 6 degrees. The plane of polarisa- 

 tion is, moreover, always nearer the horizon than the sun, while 

 the angle between the planes presents diurnal maxima and 

 minima, a point of extreme interest. The electro-magnetic rota- 

 tion of the plane of atmospheiic polarisation is distinctly proved 

 by the follow ing observation : — At noon the position of the sun 

 is such as to produce an illumination of the sky symmetrical 

 with respect to the meridian, which ought therefore to coincide 

 with the plane of polarisation ; but as a matter of fact the coin- 

 cidence of the two planes does not occur at noon, but at a later 

 hour, so that the plane of polarisation has obviously been rotated 

 through a certain angle. This rotation corresponds with the 

 results obtained by direct observation by M. Becquerel upon the 

 magnetic rotatory power of air, as regards both the magnitude 

 and the sense of the rotation. The existence of rotatory power 

 in gases is thus confirmed from a most unexpected source. 



A suggestion has been made by M. d'Arsonval for the 

 improvement of Plante's secondary batteries. M. Plante em- 

 ployed as electrodes in his secondary cells two sheets of lead 

 immersed in dilute sulphuric acid, which became spongy by use, 

 holding the hydrogen and oxygen liberated at the respective 

 poles in loose combination. The limits of the performance of 

 such cells appear to be fixed by the escape of hydrogen bubbles 

 from the kathode, and by the low conductivity of the film of 

 peroxide of lead formed over the surface of the anode. M. 

 d'Arsonval therefore proposes to obviate the one difficulty by 

 electrolysing a salt of zinc instead of a dilute acid, and the other 

 by increasing the available surface of lead at the anode. For 

 the latter he employs shot heaped about a carbon plate. The 

 liquid is a strong solution of sulphate of zinc. During the 

 charging of the cell, zinc is deposited out of the solution upon 

 the surface of a lead plate, or belter, upon a free surface of 

 mercury amalgam, suphuric acid being formed in the solution, 

 which attacks the zinc so soon as the cell is employed to generate 

 a current. Whether this modification is really an improvement 

 upon the form devised by Plante, remains to be seen. An 

 electromotive force of 2't volts is claimed for the new cell. 



Albumin is employed by M. Regnard in the place of collo- 

 dion for the purposes of microphotography, and is said to afford 

 perfect freedom from the harshness which appears inseparable 

 from the use of collodion films. 



Dr. Sydney Marsuen has discovered a substance in which 

 carbon is soluble, and from which it crystallises out partly in 

 graphitoidal, partly in adamantine forms. The adamantine 

 crystals exhibit beautiful octahedral shapes under the micro- 

 scope, and scratch sapphire readily. There seems every reason, 

 therefore, to regard them as true diamonds. 



GEOGRAPHICAL NOTES 

 At the meeting of the Geographical Society on Monday last, 

 Sir T. Fowell Buxton, after a few explanatory observations, 

 read an account of a visit to the famous I.ukuga creek in May 

 1879, by Mr. E. C. Hore, of the London Mi-sionary Society's 

 n hake Tanganyika. The result of Mr. Hore's trip 

 from Djiii across the lake is believed to be the vindication of 

 Cameron's theory that the I.ukuga creek was the long-sought 

 outlet of Lake Tanganyi a. From the Kiyanja ridge Mr. Hore 

 saw the I.ukuga, flowing westwards with a rapid stream, on its 

 way to join the Congo, until it became lost to view among the 

 hilh ofKwa, Mekito, and Kalumbi's, in Uria. Mr. Hore it is 

 well to add, was well qualified for the investigation of this matter 

 being well acquainted with currents, &c, from his former 

 experience when in the service of the Peninsular and Oriental 

 Steam Navigation Company; he is now surveyor and scientific 

 officer attached to the Mission station at Ujiji. Commander 

 Cameron stated to the meeting at some length the history of 

 Lake Tanganyika, from its discover)' by Burton, and gave in 

 detail the various theories regarding its outlet. Dr. Emil Holub 

 followed with an address on the Marutse-Mabunda empire in 

 South Central Alrica. This empire is of recent formation out of 



two peoples, the Marutse and the Mabunda, who inhabit the 

 Zambesi region near the confluence of the Chobe with that 

 river, and have their capital at Shesheke. After a few remarks 

 on their geographical position and the neighbouring tribes, Dr. 

 Holub addressed himself to the ethnographical side of his 

 subject, and gave many interesting particulars respecting the 

 people and their manners and customs. Among their peculiarities, 

 as distinguished from other South African tabes, the more note- 

 worthy are a belief in a supreme being and in a life after death, 

 and the respect and consideration in which women are held. 



The arrangements relating to the reception of Prof. Nor 

 denskjdld in France have been somewhat altered. The cele- 

 brated explorer having expressed his determination to accomplish 

 personally the periplus of the Mediterranean coasts of Europe, 

 he will proceed, via Gibraltar, to Havre, where he will be 

 received by a deputation from the Paris Geographical Society, 

 and be conducted to Paris, where he will be magnificently 

 treated. The Municipal Council of Paris has subscribed a sum of 

 200/. to the funds. It is certain that he will land at Lisbon, where 

 the Portuguese Geographical Society is preparing a reception. 

 It is said that the Geographical Society of Algiers will send a 

 requisition to Prof. Nordenskjold asking him to visit their town, 

 and witness their festive installation. He will not be present 

 at the meeting of the Academy of Sciences on March I. At 

 a large meeting of the Geographical Society of Rome, on 

 Sunday, its gold medal was conferred upon Prof. Nordenskjold, 

 who was present along with his staff. Speeches were delivered 

 in praise of the enterprise, and Prof. Nordenskjold replied 

 briefly in French. King Oscar of Sweden has ordered four gold 

 and forty-six silver medals to be struck for the officers and crew 

 of the expedition. 



The Rev. F. Coillard, of the French Basuto Mission, in 

 company with whom it will be remembered Major Serpa 

 Pinto made his journey from the Zambesi to the Bamangwato 

 country and to the Makarikari, has recently delivered a lecture 

 at Capetown, chiefly on missionary topics. He stated that he 

 had sojourned principally among a tribe known as the Banyai in 

 the neighbourhood of the Zambesi. On his journey thither he 

 had passed through a tribe which was divided into small com- 

 munities, and led a miserable life owing to the oppression of the 

 Matabele. Mr. Coillard also visited the Matabele country, of 

 which he had but a poor account to give ; the climate, he says, 

 is most unhealthy, not only for Europeans but even for the 

 natives. 



The new Bulletin of the Antwerp Geographical Society con- 

 tains a paper by Dr. L. Delgeur, entitled " Les Endiguements 

 de la Neerlande : Lutte des Hollandais contre la Mer," and the 

 text of some interesting letters which the International African 

 Association have received from East Central Africa. 



The Colonies and India gives a brief description of the mag- 

 nificent Tequendama Falls near Santa Fe de Bogota, in the 

 Colombian Republic, and draws attention to the fact that it has 

 been visited by but few English travellers. 



As supplementing No. 59 of Petermanns Mittheilungen, an 

 abstract of an itinerary in Japan, by Dr. Knipping, is published. 

 The itinerary extended from Kioto by Shimonosura to Tokic, 

 and contains much valuable information on the country traversed. 

 It is accompanied by three maps. 



No. S of Globus describes the journey of Rohlfs and Stecker 

 last summer from Battisal, south of Jalo, in Tripoli, to the oasis 

 of Kufra, which lies about half-way between the western frontier 

 of Egypt and the eastern boundary of Fezzan, and has not before 

 been visited by Europeans. The oasis of Kufra lies between 

 2t° and 24° E. and 26" and 24° S., and is happily described in 

 the map which accompanies the paper as an oasis archipelago. 

 It is represented as a series of regions covered with palms, amid 

 a country of hills and sand dunes. 



A STRANGE PHENOMENON 



'"THE following letter from R. E. Harris, Commander A. S. 

 ■*• N. Co.'s s.s. Shahjehan, dated Calcutta, January 19, appears 

 in the Calcutta Englishman of January ?.\ : — 



" The most remarkable phenomenon that I have ever seen at 

 sea was seen by myself and officers on the 5th instant between 

 Oyster Reef and Pigeon Island (Malabar coast). At 10 p.m. 

 we were steaming along very comfortably ; there was a perfect 

 calm, the water was without a ripple upon it, the sky was cloud- 



