3°4 



NATURE 



[August 31, ign 



The volumi ••< Milteilungen of ihe Berne Scientifii 

 Society for ioio contain? an interesting attempt by 

 P. Gruner to render the principle of relativity intelligible 

 to the less mathematical reader. The twenty-one pages ol 



" elementary " presentation still offer a formidable arraj 

 of complex arguments, many of which are by no means 

 easy to follow. Gruner imagines the inhabitants of earth 

 and Mars as engaged in an attempt to unify and conned 

 their respective time and space scales without the aid ol 

 astronomir.nl observations of any other bodies, but with the 

 free use of wireless telegraphy for mutual communications. 

 He shows how, owing ( relative motion, the scales must 

 differ, and deduces Einstein's transforming equations in a 

 simple manner. The scheme and argument could, no 

 doubt, be still further simplified, and the simplei the 

 better. Even this simplification tends to bring out the 

 essential weakness of the theory, which assumes that 

 successive light waves from a moving source are not eon- 

 centric, and at the same time Dostulates, on the basis of 

 Michelson's experiment, that this eccentricity cannot be 

 discovered. Everything would be so much simpler if the 

 speed of the body were added to the speed of the light it 

 emitted, a supposition which, indeed, docs not appear to 

 contradict any astronomical observations. 



Although the "exploring electrode" method of deter- 

 mining til.' distribution of electrical potential in the 

 kathode dark space of a vacuum tube through which an 

 electric disc harge is passing has been suspected for some 

 time, and has recently been superseded by the measure- 

 ment of tlic deflection of a beam of kathode rays shot 

 transversely through the discharge, it is important that 

 the reason for the divergent results obtained by the former 

 method should he ascertained. Prof. Wehnelt shows in a 

 paper in the V erhandlungen der Deutschen Physikalischen 

 Geselischafi for July 30 that any small obstruction placed 

 in tin- kathode dark space acquires a positive charge, and 

 its potential is therefore higher than that of the point at 

 which it is placed. Between tie- kathode and the obstruc- 

 tion the rise ol pot. ntial is linear, but between the obstruc- 

 tion and the kathode glow it is curved, showing that 

 electric charges are present in (his portion of the discharge. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occukpences kor September:— 

 Sept. 2. 22h. om. Saturn stationary. 



4. 4I1. 37m. Uranus in conjunction with the Moon 



(Uranus 4 35' N.). 

 9. 3I1. om. Mercury in inferior conjunction with Ihe 

 Sun. 



13. in. 4S111. Saturn in conjunction with the Moon 



(Saturn 4° 22' S. ). 



14. oh. 39m. Mars in conjunction with the Moon (Mars 



4°32'S.). 



15. oh. om. Venus in inferior conjunction with the Sun. 

 17. 9I1. 2Sm. Neptune in conjunction wiih the Moon 



(Neptune 5° 46' S.). 

 20. 23b. 11m. Venus in conjunction with the Moon 



(Venus 13 14' S.). 

 23. 1 fih. iSm. Sun enters sign of Libra. 

 25. 2h. om. Mercury at greatest elongation W. of the 



Sun (17 52'). 

 ,, i2h. om. Mercury in perihelion. 

 ,, 16I1. 5m. Jupiter in conjunct on with the Moon 

 (Jupiter 2' n' N.). 



B s's Comet, 1911c. During several of the clear 



evenings whi, h obtained at the latter end of last week, 



's comet was faintly visible to (lie naked eye of an 



observer who knew where to look for it. Ordinary opera- 



11 ' ■ showed 11 as a distinct nebulosity, and in the field 



ii-inch refractor it was a really brilliant object, some 



5 or 0' in diameter, having a distinct nucleus. On Sunday 



night, at Gunnersbury, Sir. W. E. Rolston found the 



no. 21 S3, vol. 8;] 



comet, as seen with opera-glasses, to be no less con- 

 us than u 1 Cygni (mag. 5-6), which it immediately 

 preceded. 



Encke's Comet, 191 id. — Observatioi ol I 

 made by Dr. Gonnessiat a! the Algiers Observatory, an 

 recorded in No. 4518 ol 'he Astronomische \achrichten. 



i >i Vugust 1, under excellent atmospheri ditions, thi 



comet was seen before ninth-magnitude stars whii h 

 rising at the same time, and if seen in a dark sky would 

 probably have equalled in brightness stars ol the seventh or 

 eighth magnitude. 



Dr. Backlund briefly discusses the recent observations, 

 and gives an ephemeris extending to Septembei 21. Al 

 present the cornel is apparently about 2 south-east of 



Leonis, and is travelling south of, and almost parallel 

 to, the ecliptic, down through Virgo towards Libra; on 

 September 14 it will be some 5° south of Spica. 



Tup Aspect or Nova Licert/e. — On a photograph taken 

 witli fifty minutes' exposure on August 11, Herr Kostinsky 

 found that the image of Nova Lacertae was surrounded by 

 a well-defined luminous aureole (black on tl 

 similar to that which surrounded the images of Nova 

 Persei in 1901. "Ibis aureole is not to be seen on similar 

 negatives secured in January and February ; therefore Herr 

 Kostinsky deduce, it may be taken as an indication that 

 the nova has now become a gaseous nebula in the spectrum 

 of which only bright radiations of hydrogen and the 

 nebula lines are represented. The photographic magnitude 

 of the nova on August 11 was about 105 ( Istronomische 

 Nachrichten, No. 4518). 



Kiess's Comet, 1011b. — An improved set of elements 

 and an ephemeris are given for comet 1911b, by Dr. 

 Kobold, in No. 451S of the Astronomische Nachrichten. 

 The comet reached its most southerly point on August 24, 

 and is now travelling northwards slowly. For the next 

 fortnight its apparent path lies through the constellation 

 Telescopium. This comet was discovered independently by 

 Herr Raimond Moravansky in Moravia >^t August 5, and 

 the observation sent to Kiel : but this was nearly a month 

 later than the discovery by Mr. Kiess. 



The Early Visibility op the New Moon. — From 

 calculations based on the data given b) Mr- Horner for 

 his remarkably early detection of the new moon, on 

 February 10, 1010, Mr. Whitmell finds, after correcting for 

 parallax, &c, that the difference in altitude between sun 

 and moon at the moment of observation was 

 the moon being 1° 46' above, and the sun 1° 30' below, the 

 horizon. The corrected azimuth different 9 S', 



and lie' moon's age sixteen hours, so that Ibis obsi 

 is probably unique in its detection of Hi soon 



after " new moon " (The Observatory, No. 438). 



VariadLI Sims -Observers of variable stars will find 

 part ii., vol. lv., of the Annals of the Harvard 1 

 Observatory, prepared by Miss Cannon, useful. Ii con 

 tains a table in which are set out the maxima and minima 

 of a large number oi variable stars. Fot each variable 



il lements and the dates of observed maxima and minima 



are tabulated, with a special column showing the differ- 

 ences between thi observed and calculated dates. 



In No. 4515 of the Astronomische Nachrichten Herr 

 Mi Miindler publishes the results of a number of oh 

 lions oi variable itars made by him, with a 6-inch comet 

 seeker, at Mundenheim during 1 



II iTER SUPPLY IX THE UNITED STATES. 



TO its excellent series of pamphlets on water supply 



tin- I iiii'.i States Geological Survej has jusl added 



three papers, one (No 170) descriptive of the hydrographical 



Features "I the Greal Basin, an immense tract of country 



208, square miles in area (just as largi .is Germany), 



and extending ovei parts of the States ol f tali, Nevada, 

 Idaho, Oregon, and California; (le other two, practical 

 manuals entitled, 1 spectively, "Underground Waters" 



i (Paper No. 2^S) and "Well-Drilling Methods" (Papei 

 No. 257). 



Of the lirsi pamphlet, it is only necessan (o remark 

 that it follow- on the same lines a- those adopted for 

 similar reports, recently reviewed in these columns, on 



' other of the dozen districts into which the United States 



