43& 



NATURE 



[October 7, 1909 



An interesting paper on sparks as indicators of the 

 •different kinds of steel was contributed by Mr. Max 

 Bermann, Budapest, at the meetings of the International 

 Association for Testing IVIaterials, held in Copenhagen 

 •early in September. An abstract appears in Engineering 

 for September 17, from which we learn that the author 

 stated that the influence of the emery-wheel on the nature 

 of the sparks was far outweighed by that of the quality 

 of the steel. It seems from the author's experiments that 

 the spark ray gives a precise indication of the quality of 

 the metal, and may be so applied in practice. Pointed 

 branching lines denote carbon steel (Siemens-Martin) ; 

 leafy ends of the branching lines indicate Siemens-Martin 

 steel containing a high percentage of carbon ; spark 

 -pictures, with a blossom-branch-like appearance, are 

 obtained from ordinary tool steel, and so forth. The 

 author states that the spark test is so sensitive that it 

 •gives clear indication of a difference of 001 per cent, of 

 ■carbon, and could be resorted to in the course of the 

 Siemens-Martin process for testing the bath and also for 

 the inspection of the finished material. 



Among other interesting articles in the August number 

 •of The Central, the organ of the Old Students' Association 

 of the Central Technical College, City and Guilds, is one 

 on pipes for use underground, by Mr. H. A. Humphrey. 

 In this article the writer emphasises the great value of a 

 proper covering for steel pipes. Thin bituminous coatings, 

 obtained by dipping in hot mixtures, is liable to be 

 •destroyed in places by the subsequent handling of the 

 ■pipe. What is wanted is a coating which has elasticity 

 and offers greater mechanical protection. The South 

 Staffordshire Mond Gas Company followed the recom- 

 mendation of the author for its mains, extending over 

 ■an area of 120 square miles, a great portion of which lay 

 In the " Black Country," thus rendering the mains liable 

 to subsidences and to attacks from sulphur and acid com- 

 pounds. The steel pipes were coated once with asphaltum, 

 then wrapped round with Hessian or canvas, and after- 

 wards again coated with asphaltum, the result giving a 

 thick, tenacious coating of sufficient elasticity and strength. 

 Five years' experience is now available, and has proved 

 that even under the worst conditions such a coating, when 

 properly applied, is an absolute preservative against 

 .corrosion. 



OUR ASTRONOMICAL COLUMN. 



Observations of Mars. — Further results of his observa- 

 itions of Mars are published by M. Jarry-Desloges in No. 

 4358 of the Asironomische Nachrichten (p. 224, Sep- 

 tember 24). 



Changes are becoming more numerous, and the canals 

 ■more visible. The observations made at the Massegros 

 Observatory (Causse de Sauveterre) showed a new canal 

 on Libya, but the Hellespontus was no longer visible. 

 The Indus was seen to be intercepted at the estuary of 

 the Oxus, and Syrtis Major and the Baie du M^ridien 

 were intersected. Since September 3, both at the Revard 

 and the Massegros stations, a clear band traversing the 

 Aurorse Sinus was recorded. The Revard plateau observ- 

 ing station is being dismantled before it becomes snow- 

 bound, and the instruments are to be remounted on the 

 plains of the Beauce. 



Having occasion to examine some of Prof. Lowell's 

 iqo7 photographs of Mars, M. Antoniadi was struck by 

 the absence of the dark band which, according to visual 

 observations, is circumjacent to the polar snows. Whilst 

 recognising the possibility that this may be due to the 

 photographic encroachment of the neighbouring bright 

 area, M. Antoniadi does not think that this is the probable 

 •explanation ; he would rather believe that in the visual 



KG. 2084, VOL. 8l] 



observations the phenomenon is a subjective one, the 

 appearance of a dark band being produced by contrast with 

 the bright cap. 



Some interesting letters, describing the observed pheno- 

 mena, and drawings, communicated by MM. Jarry- 

 Desloges and Antoniadi to Signor Schiaparelli, are pub- 

 lished by the latter in No. 9, vol. iii., of the Rivista di 

 Astronomia (Turin). 



The Recent Magnetic Stokm and Aurora. — From Mr. 

 Basil T. Rowswell we have received an account of an 

 auroral display observed by him, at St. Martin's, Guernsey, 

 on the night of September 25, the date of the magnetic 

 storm described in Nature for September 30 (p. 395). On 

 going into the garden a| S p.m. (G.M.T.) Mr. Rowswell 

 was struck by the appearance of a rosy glow, at an altitude 

 of about 60°, in the E.N.E. sky. this glow brightened 

 and then faded away, or was obscured by misty clouds 

 and, possibly, moonlight, until at 8.10 p.m. no trace of 

 it was to be seen ; nor could it be discerned at 9 p.m. 

 when the sky was partially clear. That it was a true 

 auroral display which he observed Mr. Rowswell has no 

 doubt, and he suggests that, had the sky been clear, a 

 good, if brief, display might have been seen at Guernsey. 



Elements and Ephemeris for Halley's Comet (1909c). 

 — A set of elements, computed by the Russian Astrono- 

 mical Society, for Halley's comet is published in 

 No. 4358 of the Asironomische Nachrichten. The pertur- 

 bations for the period November 15-9, 1835, to December 

 13, 1909, were computed by the method of mechanical 

 quadratures, and the time of perihelion passage is given 

 as 1910 April 23. An ephemeris which accompanies the 

 elements gives positions for every tenth day from Sep- 

 tember 4 to December 23, and agrees fairly well with the 

 position determined, for September 11, from Prof. Wolf's 

 photograph. 



Double-star Observations. — In No. 4350 of the Asiro- 

 nomische Nachrichten Prof. Doberck compares the 

 observations of a number of double stars, made by various 

 observers, with the data deduced from the published orbits. 

 For twenty-three objects he gives the places where the 

 orbits were published, the years in which observations 

 were made, and the differences, for each observer, in angle 

 and distance. The names of the observers are given in 

 abbreviated form in accordance with a comprehensive list 

 published by Prof. Doberck in No. 4346 of the same journal. 



A Newly discovered Nebula Cluster in Cetus. — In 

 No. 4352 of the Asironomische Nachrichten Prof. VVolf 

 announces the discoverv of a small cluster of nebulae in 

 the constellation Cetus. The position of the cluster is 

 a = 2h. 50m., 5= +54° (18550), in a region which is 

 generally very barren in these objects. The new object is 

 very faint, with a central condensation, and has a fila- 

 mentous appearance. 



Observations of Variable Stars. — No. 4352 of the 

 Astronomische Nachrichten is devoted to the discussion of 

 twenty stars of which the variability is doubtful or small. 

 The observations were made, photometrically, at Potsdam, 

 by Herr W. Miinch, during the period September, 1908, 

 to March, 1909, and are discussed at some length. 



Terrestrhl Refraction in Egypt. — No. 33, vol. iii., 

 of the Cairo Scientific Journal contains an interesting dis- 

 cussion of some observations of vertical refraction made 

 by Mr. Xvdis at Alexandria. The observer found a well- 

 marked diurnal variation which, in November, 1908, gave 

 for /,•, the coefficient of refraction, values ranging from 

 00497 (at oh.) to 01186 (at i7h.) ; frequently the value, 

 which is usually positive, was found to be negative. The 

 observations are also discussed by Messrs. Craig and 

 Keeling, the latter pointing out the difficulties inherent to 

 observations of vertical refraction, especially when settings 

 are made on a sea horizon. Observations made at Helwan 

 Observatory in November, 1908, showed the refraction to 

 vary between 0-781 and o-ioi, and, when compared with 

 others made in June, showed that h is much smaller in 

 summer than in winter, the values ranging, in June, from 

 o 368 to 0076. It also appears that the refraction in 

 Egypt varies much more than in European countries. 



