78 



NATURE 



\_Nov, 28, 1878 



conclusion of Dr. C. E. Jung's Contributions to the 

 Geography of Victoria ; an important paper, with 

 map, on the Chinese province of Kwang-tung and its 

 people, by Herr J. Nacken ; another on D'Atbertis' New 

 Guinea Exploration, with map of the Fly River ; with 

 papers on the Exploration of the Ogowd, Nordenskjold's 

 Voyage in the Vega, and Dr. Behm's monthly summary. 

 Thus it seems that Dr. Behm, the new editor, is likely 

 to maintain the reputation and value of this, the most 

 important geographical organ. 



The October Bolletina of the Italian Geographical 

 Society contains a short account of the Progress of the 

 Itahan African Expedition, and letters from Lieut. Bove 

 who accompanies Prof. Nordenskjold in his North-East 

 Passage Expedition. In the Bulletin of the Paris Society 

 is a translation of the Grand Duke Nicholas's paper on 

 the Shortest Route for a Railway to Central Asia ; a paper 

 by M. L. Simonin on the Indians of the United States, 

 with a map showing the Indian reservations ; the con- 

 tinuation of Dr. Decugis' Account of his Journey in Mo- 

 rocco ; a long article by the Abbd Manager on Guinea, 

 besides shorter papers on a Uniprojectional Atlas, and 

 the Rio Casca of Peru. 



The Portuguese African expedition, under Serpa 

 f into, which left Benguela a year ago, reached Bihd in 

 March last, and was to enter the unknown interior in two 

 divisions. The Lisbon Geographical Society are moving 

 Government for a scientific expedition into Portuguese 

 Senegambia. 



ON SOME IMPROVED METHODS OF PRO- 

 DUCfNG AND REGULATING THE ELECTRIC 

 LIGHT ' 



AMONG the manifold functions which the elementary 

 substance carbon performs in organic nature, not 

 the least important is that by which it becomes the great 

 source of artificial illumination, whether derived from 

 x)ils, coal gas, or from coke rendered incandescent by the 

 action of powerful electric currents. Since the time 

 when Davy first produced the voltaic arc, between two 

 points of wood charcoal, through which was transmitted 

 the current from the great batteiy of 2,000 plates belong- 

 ing to the Royal Institution, many experiments have been 

 made to determine the best kinds of carbon for develop- 

 ing the electric light. The carbon which, until recently, 

 was most commonly employed for this purpose, is ob- 

 tained from the sides of gas retorts, where it accumulates 

 in the form of coke during the destructive distillation of 

 coal. The shells of coke from the retort are sawn up 

 into pencils from one quarter to half an inch square, and 

 from six to nine inches in length. Although very good 

 results are obtained from carbon of this kind, it is a 

 difficult material to work on account of its hardness, and 

 it sometimes contains impurities which interfere with its 

 conductivity. It is also liable to fracture when suddenly 

 heated by the transmission of powerful electric currents. 

 These defects have led to the introduction in electric 

 lighting of artificial carbon, composed of powdered coke 

 and lampblack, formed into a paste with molasses and 

 gum. This material is pressed into cylindrical forms, 

 and subjected for a given time to a high temperature in a 

 special furnace. The manufacture of these carbon pencils 

 has attained great perfection in the hands of Carrd, of 

 Paris, and they can be made into perfectly straight and 

 cylindrical forms of from two to sixteen millimetres in 

 diameter, and half a metre in length. 



When the electric light is to be used for illumination, it 

 is necessary that it should be as continuous as other modes 

 of lighting. For this purpose not only should the current 



* Paper real by Mr. Henry Wilde at the Manches'.er Literary and 

 Philosophical Society, October 29. 



be regular in its action, but the distance between the carbon 

 points must not alter, which necessitates the use of some 

 arrangement for bringing them nearer together in propor- 

 tion as they are consumed. Much ingenuity has been 

 displayed by electricians in solving this problem, and the 

 automatic contrivances invented by Staite, Duboscq, Fou- 

 cault, Serrin, and others, leave little to be desired in regard 

 to the steadiness of the light, when the regulators are in 

 good order, and in the hands of intelligent operators. All 

 automatic instruments, however, from the delicacy of their 

 mechanism, are Uable to derangement, and their action is 

 not easily understood by persons not having a special 

 knowledge of their construction. To obviate the objection 

 to the use of such instruments by unskilled attendants, I 

 devised, a few years since, a regulator for use on H.M.'s 

 ships of war, to be actuated by hand. In this arrangement 

 the carbons are made to approach and separate from each 

 other by means of a right and left-handed screw connected 

 with the carbon holders. Each of the screws, with its 

 carbon holder, can be actuated independently of the other, 

 for the purpose of adjusting the points of the carbons to the 

 proper focus of the optical apparatus used in connection 

 with it. The regulator, with its carbon points, is placed in 

 the focus of a dioptric lens, which parallelises the diver- 

 gent rays of light into a single beam of great intensity. 

 The lens with the regulator is pivoted horizontally and 

 vertically on the top of a short iron column, fixed on a 

 raised platform above the deck, and the beam of light 

 may be projected upon any distant object within its range. 

 This special application of the electric light, however, as 

 will be seen, requires the frequent adjustment of the 

 carbons by the operator, but as he is always required to 

 be in attendance to manipulate the projector, no incon- 

 venience is experienced through the absence of the auto- 

 matic arrangement. This method of reg^ilating the 

 electric light has now been in use in the Royal Navy for 

 more than three years, and has proved very satisfactory. 



Simultaneously with the progress of improvements in the 

 mechanism for regulating the electric light, experiments 

 have been made with the object of dispensing with the 

 regulator altogether. The most recent, as well as the most 

 successful, of these attempts has been made by M. Jabloch- 

 koff, a Russian inventor. In the specification of his letters 

 patent of 1877 he proposes to place the carbons side by 

 side (as had been previously proposed by Werdermann in 

 1874), and to separate them by an insulating substance to 

 be consumed along with the carbon. The inventor states 

 that the insulating substance for separating the carbons 

 may be kaolin, glass of various kinds, alkaline earths, and 

 silicates, which he prefers to apply in the form of powder 

 rammed into an asbestos cartridge-case containing the 

 carbons. A powder which the inventor found serviceable 

 consists of one part lime, four parts sand, and two parts 

 talc. These materials are rammed into the cartridge-case 

 surrounding and separating two parallel sticks of carbon 

 placed in the case, at a little distance apart. One of the 

 carbons is made thicker than the other to allow for its more 

 rapid waste. The lower ends of the carbons are inserted 

 into pieces of copper tube or other good conductor, sepa- 

 rated from one another by asbestos, and the ends of the 

 tubes are pinched between two limbs of a screw vice, con- 

 nected respectively to the conducting wires. This combina- 

 tion of carbons and insulating materials the inventor terms 

 an electric candle, which, when mounted on a stand or 

 candle-stick, has the appearance of the Roman candle of 

 pyrotechnists. The inventor further states that the heat 

 produced by the electricity fuses the material between the 

 carbons and dissipates it ; and the freedom of the passage 

 afforded by the fused material to the electric current 

 permits the subdivision of the light by placing several 

 lamps in the course of one electric circuit. It is also 

 stated that the construction of the candle may be varied ; 

 and, among the forms described, is one in which the 

 carbons, instead of being contained in a cartridge case> 



