628 



NATURE 



[February 6, 19 13 



temperatures up to 550° C, which appeared in the 

 Zeitschrift of the Association of German Engineers 

 last year. The work is based on the experimental 

 determinations of the specific heat of steam made by 

 Knoblauch and Jakob and by Knoblauch and Mollier. 

 From these values the author, by a graphical method 

 which solves the thermodynamic equation connecting 

 the rate of increase with pressure of the specific heat 

 at constant pressure with the rate of increase of the 

 expansion with temperature, determines the specific 

 volume over the range stated in the title of his paper. 

 Up to eleven atmospheres and 190° C. the calculated 

 values agree closely with the observations of Linde, 

 so that it seems probable that they may be trusted 

 over the much wider range covered by the author. 



The second lecture on chemistry in gasworks, 

 arranged by the Institute of Chemistry, was delivered 

 by Mr. VV. J. A. Butterfield, on January 31, at 

 University College. Mr. Butterfield showed that the 

 sensitiveness of lead acetate paper as a test for the 

 presence of sulphuretted hydrogen varies inversely 

 with the area of the paper exposed to the gas. The 

 sulphur impurity remaining in gas after the extraction 

 of sulphuretted hydrogen, he considers to be objection- 

 able on account of its destructive action on the metal- 

 work of inverted burners and fittings directly exposed 

 to the undiluted products of combustion of gas. In 

 connection with the by-products of gas manufacture, 

 he stated that the predominant uses of tar at present 

 are for the production of pitch for the supply of the 

 patent-fuel industry of South Wales, and for road 

 construction and treatment. Physical tests of tar and 

 pitch are misleading as to the value of these materials 

 for the latter purpose, because the physical character- 

 istics change with efflux of time, and the extent and 

 bearing of the changes which thus occur in tar and 

 pitch can be ascertained onlv by appropriate chemical 

 examination of them. Mr. Butterfield directed 

 attention to the acceptance practically everywhere, 

 except in German-speaking countries, of the Harcourt 

 lo-c.p. pentane lamp as the reference standard of 

 light for all photometric work. The secondary elec- 

 tric standard lamps are calibrated by comparison with 

 it Comparative tests have been made of the light 

 afforded by about 150 different specimens of the Har- 

 court lo-c.p. lamp, and a disagreement by more than 

 0-2 per cent, has never been found, except in cases 

 where there has been a fault in construction. 



At the sixth congress of the International Asso- 

 ciation for Testing Materials, held in New York last 

 September, fifteen papers were submitted dealing with 

 impact and endurance tests. These are summarised 

 by Dr. W. Rosenhain in The Engineer for January 31. 

 In drawing conclusions, Dr. Rosenhain states that the 

 general feeling at the congress was not in favour of 

 introducing impact tests into specifications as yet. 

 While enough has been done to show that some form 

 of impact test is desirable, there is a lack of consistent 

 results from different machines and different forms of 

 test pieces. It is evident that what is now required 

 is carefully directed research by many independent 

 workers with the view of clearing up the causes of 

 discrepancies. Further progress in mechanical test- 



NO. 2258, VOL. go] 



ing by dynamic methods should be sought by simplify- 

 ing the test conditions as much as possible, and by 

 arranging the experiments in such a way as to isolate 

 and measure one single physical property or constant 

 of the material, rather than by any attempt to imitate 

 in the laboratory the complex conditions of practical 

 use. 



A COPY of the Almanac of the Egyptian Govern- 

 ment for 1913 has been received. In addition to full 

 particulars of the various Government departments, 

 the Almanac contains valuable meteorological, mag- 

 netic, and other scientific data. 



A COPY has been received of a new, revised, and 

 enlarged edition of the pamphlet published in 1908 

 by Ilford, Ltd., giving notes on the Ilford X-ray 

 plates. Scientific workers desiring to possess copies 

 of the pamphlet, which is effectively illustrated, may 

 obtain them, free of charge, on application to the 

 company at Ilford. 



OUR ASTRONOMICAL COLUMN. 

 Comet 1912a (Gale). — Gale's comet, discovered in 

 September last, is now a circumpolar object, of about 

 the tenth magnitude, in our latitudes. From the 

 following ephemeris, abstracted from a daily 

 ephemeris published by Dr. Ebell in No. 4627 of the 

 Astrononiische Nachrichten, it will be seen that the 

 comet is now travelling southwards through Cassio- 

 peia, and may be observed high up in the west during 

 the evening. 



Ephemeris I2h. M.T. Berlin. 



Feb. 7 



3 151 

 3 42-1 



15 



+ 78 45 

 + 76 24 



+ 74 7 



Feb. 19 



Observed by Herr G. 



4 172 . +71 56-2 

 23 ... 4 29-q ... +6q 517 

 27 ... 4 40-6 ... +67 54-3 



van Biesbroeck at Uccle 

 between January 4 and 9, the magnitude of the whole 

 comet was about 90, and the diameter, observed in 

 a finder, was about 10'. In No. 4625 of the Astro- 

 noinische Nachrichten, Herr Moschonkin directs 

 attention to the similarity between the elements for 

 Gale's comet and those for a comet which appeared 

 in 1672. 



The Expected Return of Finlay's Short-period 

 Comet. — With a period of 6-5 years, the comet dis- 

 covered by Finlay at the Cape in 1886 is shortly due 

 at perihelion. According to elements previously cal- 

 culated bv M. Schulof, perihelion passage should take 

 place on March 24, but the comet passed very near to 

 Jupiter in the summer of 1910, and, from a study of 

 the perturbations, M. G. Fayet finds that perihelion 

 has probably been advanced by about six weeks. His 

 new elements, published in No. 4626 of the Astro- 

 noniische Nachrichten, give February 6 as the date 

 and he gives three search-ephemerides based on the 

 assumptions that perihelion would be passed on 

 February 6, January 29, and February 14 respectively. 

 The first gives the present position as lying in 

 Aquarius very near the western horizon at sunset. 

 At no time during this apparition will the comet be 

 an easy object, chiefly owing to its apparent proximity 

 to the sun, but it may be rediscovered by means of 

 one of the powerful instruments now available ; during 

 February the theoretical brightness is about that at 

 the time of the comet's discovery. 



The Magnitude Variations of Nova Geminorum 

 No. 2. — A large number of observations, made at 



