January 20, 19 16] 



NATURE 



575 



g-yroscope then exerts a powerful restoring couple on 

 the frame of the ship. The arrangement appears to 

 have been very successful, and rolls of 25° on each 

 side of the vertical have been quenched to 3°, the 

 quenching being accompanied by much steadier steer- 

 ing. By no means the least interesting part of the 

 paper is the collection of accompanying photographs 

 and drawings of the arrangement ; some of the latter 

 are from working drawings, and enable the construc- 

 tion of the gyroscope to be understood perfectly. 



Dr. J.'E. Stead has collected the results of analyses 

 of a large number of German shells and has given 

 them recently in a paper read before the Cleveland 

 Institute of Engineers, and reported in the Engineer 

 for January 14. Dr. Stead discusses our own specifica- 

 tions for shell steels. The actual tests applied to such 

 steels are confidential, but it is of interest to note that 

 Dr. Stead, speaking as an analytical chemist, is of the 

 opinion that no shell steel should be rejected on the 

 results of chemical analysis provided the mechanical 

 tests are satisfactory. Our enemies are not particular 

 in having shell steel of uniform quality ; the steel used 

 is generally of relatively high tenacity, and is much 

 more liable to break up by shock than what we pro- 

 duce and prescribe. It is most probable that some of 

 the German shells are made by the basic Bessemer 

 process, judging from the relatively large amount of 

 nitrogen present in one of the toughest and best frag- 

 ments, which also contained 007 per cent, of sulphur 

 and phosphorus. The analysis of armour-piercing shells 

 agrees with that of similar material made in other 

 countries. German shells with between 0-07 and o-i 

 per cent, of phosphorus did not burst in the gun, hence 

 it seems probable that great freedom from that element 

 has been found to be unnecessarv. 



OVR ASTRONOMICAL COLUMN. 



Comet 19156 (Taylor). — There continues to be a 

 dearth of information regarding this comet. Its actual 

 position now differs very considerably from the only 

 ephemeris available. Thus on January 13, ii.o p.m., 

 an observation made at the Hill Observatory showed 

 that the ephemeris required corrections of +40 min. 

 in R.A., and —1° 15' in declination. The comet was 

 easily seen in spite of strong moonlight, and was 

 bright enough to show the cross wires in the eyepiece. 



Employing observations made at Rome, December 5, 

 Bergedorf, December 18, and on Januarv 3^ 1916, at 

 Bamberg, M. J. Braae and Mile. J. Vinter-Hansen 

 have calculated the following elliptical orbit and 

 ephemeris : — 



Epoch iqi6, January 05 G.M.T. 



Mo = 355 15 49-3 (f) =32 54 206" 

 « =354 39 376 fJL =564-209" 

 Q =113 57 46-5 Log 0=0532378 

 / -= 1528 91 T -1916 Jan. 307205 G.M.T 

 U =229702d (6-29 years).' 

 i2h. G.M.T. 



R.A. D.c. 



h. m. s. 



Jan- 20 ... 5 8 39 ••• +15 47'2 



22 ... 9 38 ... 16 383 



24 • •• 10 49 ... 17 28-9 



26 ... 12 12 ... 18 i8c) 



28 ... 13 48 ... K) S[ 



NO. 2412, VOL. 96] 



The comet's distance from the earth has been slowh' 

 increasing. The comet is stated to be about eleventh 

 mag'nitude. 



Comet 19 15^ (Mellish). — We are informed by Prof. 

 Itdwin B. Frost, director of Yerkes Observatory, that 

 Mr. John E. Mellish has taken up residence there 

 as volunteer research assistant. Comet 1915^ was 

 found with the 6-in. comet seeker, and Prof. Georges 

 Van Biesbroeck, who is spending the year at Yerkes 

 as visiting professor of practical astronomy, sub- 

 sequently obtained the accurate positions of the comet 

 using the r2-in. telescope and filar micrometer (see 

 Nature, December 2, 1915). 



MiRA Ceti. — American observations of this variable 

 star during the 1914-15 cycle show that from a mini- 

 mum of 9-0 mag. on October 15, 1914, the brightness 

 increased to a maximum of 36 on February 11, 1915. 

 By August it had again fallen to nearly 90 mag. 

 {L' Astronomic, December, 1915). With regard to the 

 present maximum, unless undue weight be given to 

 an observation made on December 27 through a 

 momentary rift in clouds, this star did not quite attain 

 to the magnitude of o Ceti (2-7). Although it is still 

 the next brightest star in the region, it now appears 

 distinctly weaker than at the beginning of the year. 



Second Type Stars of Low Density. — At the pre- 

 sent time the crucial evidence on the question of 

 stellar evolution is stellar density. Numerical data 

 accumulates which more and more insistently pro- 

 claims the existence of stars extremely different in 

 mean density, yet capable of giving rise to almost 

 identical spectra. As these data result from compli- 

 cated calculations of orbital elements, Dr. H. Shapley 

 has successfully sought for a method of deriving 

 limiting mean densities merely from length of period 

 and the duration of eclipse. The results obtained bv 

 this direct method are in close agreement with those 

 already published in his "Orbits of Eclipsing 

 Binaries" (Proc. Nat. Acad. Sci., vol. i., p. 459). 



The Distribution of Spectroscopic Binaries of 

 Class M. — To the already long list of objects show- 

 ing a preference for low galactic latitudes must now 

 be added the spectroscopic binaries of class M 

 (Antarian). C. D. Perrine {Astrophys. Journ.. xlii., 

 p. 370), dealing with ten such binaries, finds the 

 average galactic latitude is 9°, whilst omitting one 

 (13 Andromeda?), the average sinks to 7°. Orbits are 

 available for only o Orionis and o Scorpii. Com- 

 parison with the Cepheid variables discloses some 

 significant resemblances and differences, e.g., light 

 variations, small proper motions, and for the two 

 known orbits the masses of the secondary bodies are 

 similar, whilst some of the differences "pointed out 

 are the large value of o sin i, and consequently periods 

 measured in years instead of days. 



Report of the Nizamiah OBSERv.vroRY.— The annual 

 report (1914-15) of the Nizamiah Observatory (director, 

 Mr. R. J. Pocock) shows that work on the astro- 

 graphic chart has been actively advanced both as 

 regards number of plates secured with the recently 

 installed astrographic equatorial, and their measure- 

 ment, although, through illness, the director had un- 

 fortunately to spend some weeks in hospital. 



The Variable Nebula, N.G.C. 6729.— There is very 

 little definite information of the light variations of 

 nebula-, notwithstanding the great importance of the 

 matter. Perhaps this apparent neglect is merely a 

 measure of the atmospheric humiditv where most 

 observational work has hitherto been carried on. At 

 Hehvan, however, Mr. Knox Shaw has been able to 

 make ri good beginning with a photographic study of 

 the well-known nebula N.G.C. 6729— the fan-shaped 



