492 



NATURE 



[August 21, 19 19 



negligible, 

 acts thus : 



They suggest that the chlorochromate 



KClCrOj + 2Ag= KAgSOj + AgCl, 



and that as only the silver chloride is reduced by the 

 developer, the amount of silver available for the pro- 

 cess is halved by each application of it. They have 

 not, however, yet proved that the double sulphite is 

 produced and that it resists the developer, and they 

 are carrying their investigations further in" this 

 direction. 



During the last few years the use of electric heating 

 appliances has become common in the laboratory and 

 workshop owing to the production of trustw'orthy 

 heating elements. In most of these an alloy, capable 

 of resisting oxidation at iioo° C, is wound round 

 a tube or muffle, in the interior of which a tempera- 

 ture of 1000° C. can be attained. The small electric 

 furnaces exhibited by Messrs. A. Gallenkamp and 

 Co., Ltd., at the recent British Scientific Products Ex- 

 hibition of the British Science Guild illustrated the 

 numerous purposes for which such articles may be 

 used with advantage, and were of satisfactory design. 

 For heating small articles, or for estimating the 

 amount of carbon in steel by combustion, the heating 

 chamber consists of a silica tube 1-2 in. in diameter 

 and 12-20 in. long, the power required to maintain a 

 temperature of 1000° C. ranging from 400 to 800 watts. 

 For laboratories in which many estimations of carbon 

 in steel have to be made daily, two- or four-tube 

 furnaces are constructed to facilitate rapid working. 

 A special type, wound in sections capable of separate 

 heating, is provided for organic combustions. For 

 incinerations, the hardening of small steel articles such 

 as taps, dies and gauges, etc., the muffle type of fur- 

 nace is used, the dimensions of the largest made being 

 14x7x5 in., consuming 2300 watts. Messrs. Gallen- 

 kamp 's furnaces are designed so that a new heating 

 element can easily be inserted by the user, thus 

 avoiding delay in the case of a winding burning out. 

 Special attention is also paid to efficient lagging, and 

 the casing and supports are strong and durable. Re- 

 sistances for controlling the temperature are supplied 

 with each furnace. A further commendable feature is 

 that a purchaser may procure a furnace to suit his 

 own work, and is not compelled to take one of the 

 ordinary stock patterns. 



The following new books of science are an- 

 nounced : — By Messrs, George Allen and Unwin, Ltd, 

 — "Mineral Resources of Georgia and Caucasia," D. 

 Ghambashidze ; "The Equipment of the Workers," 

 "The Education of the Workers," and "The Environ- 

 ment of the Workers." By Mr. Edward Arnold — 

 "Ions, Electrons, and Ionising Rays," Dr. J. A. 

 Crowther; "Surveying," W. N. Thomas; "Tacheo- 

 meter Tables," Prof. H. Louis and G. W. Gaunt; 

 "'The Principles of Electrical Engineering and their 

 Application," Prof. Gisbert Kapp, vol. ii. ; "Examples 

 in Electrical Engineering," J. S. Gill and F. J. Teago; 

 and "Algebra for Engineering Students," S. East- 

 wood and J. R. Fielden. By Messrs. W. Hcffer and 

 Sons, Ltd. (CM^nhridfie) — "Groundwork of Surgery for 

 First-year Students," A. Cooke. By Messrs. Crosby 

 Lockwood and Son — " Electric Spark Ignition in In- 

 ternal Combustion Engines," J. D. Morgan; and new 

 editions of the "Mechanical Engineer's Pocket-Book, " 

 the late D. Kinnear Clark, revised and enlarged by 

 H. H. P. Powles; and " Hand Sketching for Mining 

 Students," G. A. Lodge and N. Harwood. By Messrs, 

 Methuen and Co., Ltd. — "Coal Mining and the Coal 

 Miner," H. F. Bulman. By Messrs. Seeley, Service, 

 and Co., Ltd. — "Chemistry and its Mysteries: The 

 Story of what Things are made of. Told in Simple 



NO. 2599, VOL. 103] 



Language," C. R. Gibson, and "The Marvels of 

 Photography : Describing its Discovery and Many of 

 its Achievements," C. R. Gibson. By Messrs. 

 Witherby and Co.— "A Geographical Bibliography of 

 British Ornithology," H, Kirke Swann, W. H. 

 Mullens, and F. C. R. Jourdain; "A Handbook to the 

 Vertebrate Fauna of North Wales," H. E. Forrest; 

 "Meteorology for All," D. W. Horner; "The Birds 

 of France," C. Ingram; and "Monograph of the 

 Pheasants," W. Beebe, vol. ii. 



OUR ASTRONOMICAL COLUMN. 



Kopff's Comet 1906 IV. = 1919a.— M. Ebell has pub- 

 lished (Ast. Nach., 4996) an ephemeris of this comet 

 from Dr Zappa's elements '{A.N., Bd. 194) with 

 a correction of +23-48' to the mean anomalv. The 

 observations made during the month show a" correc- 

 tion to this of about -7' in declination. The following 

 positions (for Greenwich midnight) include this cor- 

 rection :— 



Log J, 



9942 



9-973 

 The computed brightness decreases from magnitude 

 10-9 to ii-i during this period. The comet passed 

 through perihelion on June 28 last. 



OCCULTATION OF SmALL StARS BY JUFITEK. — Mr. 



Arthur Burnet sends particulars of two phenomena 

 of this kind that he predicts will happen in the 

 coming months. The star B.D. +18° 2062, mag. 89, 

 R.A. 8h. 46m. 52s., dec. 18° 23' 22" N., will be 

 occulted on September 15 between i4h. 15m. and 

 i5h. im. G.M.T. As Jupiter will rise at Greenwich 

 at i3h. 30m. on that night, the possibility of successful 

 observation from this part of the world is doubtful. 

 On Octobe- 5 the star B.D. +17° 2007, mag. 7-8, 

 will be occulted before 11 o'clock G.M.T., when it 

 will not rise at Greenwich until after midnight. The 

 occupation may be visible in India from roh. 25m. to 

 iih. 36m. Apparent placet of the star on October 5, 

 R.A. 9h. im. 46s., dec. 17° 26' 2" N. 



A Magnetic Storm. — The traces on the sheets of 

 the magnetographs at Greenwich showed violent dis- 

 turbance on Monday, August 11, beginning about 

 7 o'clock in the morning and lasting for twenty-four 

 hours. From notes in the daily Press it appears that 

 telegraph lines and cables were affected, and that 

 operators experienced much difficulty due to earth 

 currents. There was a spot on the sun at the time, 

 not of the largest size, but about 500 millionths of 

 the visible surface in area, which had passed the Jfl 

 central meridian on August 8. There was also a iH 

 broken group of small spots following this, and * 

 another regular spot rather less in area than the first 

 was approaching the central meridian. 



The Recent Solar Eclif^se. — Though the observers 

 of the British expedition to the Island of Principe 

 were not favoured with speciallv fine weather, some 

 useful results were obtained. Ten of the plates ex- 

 posed were spoiled by cloud so far as the object of 

 the expedition was concerned, but give an excellent 

 representation of the large prominence which was en 

 the sun's limb at the time. The remaining six photo- 

 graphs show k' andi k^ Tauri and two or three other 

 stars. The measurement of these should show the 

 looked-for deflection if it exists. 



