532 



NATURE 



{April lo, 1879 



irregularities following no law so far discovered occa- 

 sionally presenting themselves. This is particularly evi- 

 dent if we compare Argelander's last formula in vol. vii. of 

 the Bonn observations with the observed times of maxima 

 during the last fifteen years. The place of the true x 

 Cygni of Bayer, which is the variable, is, for i88o"o, in 

 RA. iQh. 4Sm. STl%.. N.P.D. 57° 23' 18"; it therefore 

 follows the star to which Flamsteed attached this letter, 

 4m. 4s., and is south of it 50' '6 ; Flamsteed' s star ought 

 to be called by his number, 17 Cygni. At the times 

 when he was looking for Bayer's x> as Argelander has 

 remarked, the variable would be near a minimum ; hence 

 his observing the nearest star of similar brightness. 



The Minor Planets in 1879.— Advanced sheets of 

 the Berliner astronomisches Jahrbuch for 1881, contain- 

 ing places of the small planets during the present year 

 have been circulated amongst observers, the ephemerides 

 for the planets coming into opposition early in the year, 

 some time since. There are positions of the first 187 

 members of this group, with the exception of Nos. 99 

 and 155, for which sufficient data are not available. Only 

 two out of the number approach the earth at opposition, 

 within her mean distance from the sun : his, on June 20, 

 is distant 0-995, with a south declination of 25°, and 

 Hertha, on September 12, 0*988, just upon the equator. 

 No. 154 travels as far south as 50^° about July 14. 



Brorsen's Comet. — The observations of this comet 

 made at Arcetri and Kremsmunster from March 10 to 19 

 with Dr. Schulze's other elements, fix the time of peri- 

 helion passage to about March 30'57i6 G.M.T., which is 

 nearly twelve hours later than that assigned by calcula- 

 tion. The following ephemeris is founded upon this 

 corrected epoch for arrival at perihelion : — 



For xzh. Greenwich M.T. 



EDISON'S LAMP 



A COMMUNICATION in yesterday's Daily News, 

 from a New York correspondent of that paper, 

 gives a glowing, and to all appearance justifiably so, 

 account of Mr. Edison's success in attaining a form of 

 electric lighting that seems to be in all respects much 

 superior to anything hitherto produced. The first im- 

 pression made on the correspondent was the mild effect 

 of the light on the eyes, its steadiness, and the absence of 

 that ghastly hue which seems to be an invariable accom- 

 paniment of the carbon. This new form of light has 

 only been attained after many disappointments on the 

 part of Mr. Edison, who, however, has all along been 

 confident of success. 



During the past two months the progress towards its 

 present perfection has been very rapid. Chiefly contri- 



buting to this result has been the discovery of a new alloy, 

 the fusing-point of which is much higher than either 

 platinum or iridium, in fact, than any known metal. 

 This discovery is spoken of by some of Mr. Edison's 

 chief employes as the greatest achievement of his life. 

 This alloy also reduces the cost of the valuable metals 

 used in each lamp to such a point as to do away entirely 

 with Prof. Tyndall's criticism. It is said to possess 

 properties heretofore unknown, or at least undefined by 

 scientific men. Not only has it cheapened the cost, but 

 the union of the metals has increased the illuminating 

 power to such a degree that six lights are now obtained 

 per horse power where only four were possible with the 

 pure platinum coil. Six lights per horse-power is the 

 number authoritatively stated, but Mr. Edison's chief 

 assistant does not hesitate to predict that eleven lights 

 will eventually be obtained for each horse-power. This is 

 not expected from the Gramme machine, however, which 

 is now used ; but is hoped for after the completion of the 

 new generator, which a dozen of the most skilled workmen 

 at Menlo Park are now engaged in constructing. 



The lamp itself takes many forms. In some instances 

 it is attached to the wall, like a gas bracket, and in many 

 others it hangs from the ceiling and takes the external 

 form of a glass globe, capped by brass or nickel attach- 

 ments. There is none of the hissing, sputtering, and 

 flickering observable in the carbon lamps. The lamp 

 which attracts most attention is, in appearance, a St. 

 Germain student lamp, without the reservoir for the oil. 

 It stands in the middle of a small table, and two fine 

 covered copper wires alone connect it with the main con- 

 ducting cables from the Gramme machine. In this the 

 Daily News correspondent tells us, are embodied all 

 the latest improvements. He also tells us that there 

 cannot possibly be any mistake, as Mr. Edison has 

 taken crucial precautions in all directions. There is 

 nothing in the lamp itself that gives any idea of its con- 

 struction. The cunning device for rendering the flame 

 steady is in reality the idea of the quadruplex telegraph 

 applied to heat instead of electricity. Now that the new 

 alloy has been discovered, its twofold purpose of preventing 

 fusion and steadying the light is no longer served. The 

 expansion of the tiny key, or switch, breaks the current 

 for the fraction of a second, and permits the actual, though 

 imperceptible, cooling of the incandescent coil. This 

 connection is made and broken many times during each 

 second, so that to human eyes the light is constant as 

 the sun. The movement of a finger and thumb converts 

 the glowing meteor before us into a night lamp for a sick- 

 room. Again, it is seen at one-candle power, then at two, 

 and so on. It is as manageable as a tallow dip, and 

 much more satisfactory. It will not go out of itself, and 

 needs no care. The little coil of wire is hermetically 

 sealed in the glass chamber. It is not in a vacuum, but 

 the chamber is filled with air. There is a sensitive spot 

 on the metal cap in which the glass tube sits, and the 

 expansion of the air manipulates the switch. The heat 

 of the metal itself, therefore, is no longer relied on. The 

 inventor explains that after all manner of severe tests this 

 has been found the easiest and the least easily deranged 

 manner of controlling the light. The difficulty of makmg 

 thin plates of metal of equal density and weight rendered 

 the previous method impracticable for small lights, al- 

 though it will probably be the best form in which to secure 

 the desired result where the lamps are to show lights of 

 great intensity. ^ 



As there seems no reason to distrust the evidence ot 

 the Daily News correspondent, it may be accepted that 

 Mr. Edison has succeeded in going a long way to solve 

 some of the difficulties connected with the practical adop- 

 tion of electric lighting. It is stated that in a few 

 months the Edison Company will be prepared to supply 

 the light to such private consumers as may desire it at at 

 least one-third or one-fourth the cost of gas. 



