October 28, 1909] 



NA TURE 



529 



Hamilton observations of September 12, 13, and 14, that 

 perihelion should occur at 19 10 April 18-63 G.M.T., and 

 that the nearest approach to the earth should take plaie 

 on 1910 May 19 at a distance of about 014, i.e. about 

 13,000,000 miles. Further, he points out that on May 

 iS-i4d. (G.M.T.) the earth and comet will be in helio- 

 centric conjunction in longitude, the longitude being 

 236° 48' ; the heliocentric latitude of the comet will then 

 be —7', so that, according to the present elements, no 

 actual transit of the comet over the sun's disc will occur, 

 but a slight change in the elements might produce one. 

 " At any rate," he says, " it seems highly probable that 

 we shall on May iS be inside the tail." 



In a communication to the Times (October 25), Prof. 

 Newall announces that he observed the comet, visually, 

 with the 25-inch refractor, power 214, on October 21. The 

 magnitude was about 14-0 or 14-5, and the faint nebulous 

 patch had neither stellar nucleus nor definite borders ; the 

 diameter was estimated as 10 or 12 seconds of arc. 



At the previous apparations, in 1759 and 1835, the comet 

 was first seen 77 and 102 days, respectively, before peri- 

 helion ; Prof. Newall 's observation was made about iSo 

 days before the calculated perihelion passage of iqio, but 

 he points out that this does not necessarily mean that the 

 comet is so much brighter at the present apparition, ior 

 he would probably not have detected it had he not known 

 its exact position as indicated by the previous photographic 

 observations. 



QUANTITAIIVE Me.ISURES OF THE OxYGEN B.WDS IN THE 



Sr-ECTRUM OF Mars. — In Bulletin No. 41 of the Lowell 

 Observatory Prof. V'ery describes tire methods by which 

 he measured the relative strength of the B, o.xygen, band 

 in the spectrum of Mars, and discusses the results in their 

 relation to the presence of, and quantity of, o.xygen in the 

 planet's atmosphere. 



.^s Prof. X'ery points out, the B band is normally so 

 intense, by the absorption in the earth's atmosphere, that 

 only by a method capable of the minutest accuracy could 

 it be expected that any slight extra intensification, due to 

 the Martian atmosphere, would become measurable. He 

 claims that, over a long series of measures, his improved 

 spectral-band comparator is capable of measuring this 

 added intensification. Briefly, although a visual examina- 

 tion shows no increase of intensity of B in passing from 

 the spectrum of the moon to that of Mars, the comparator 

 measures are surprisingly concordant in showing a positive 

 value, in favour of Mars, several times greater than the 

 probable error ; B, in the spectrum of the planet, is 15 per 

 cent, stronger than in the lunar spectrum, and the prob- 

 able error is i-8 per cent. There is, as would be expected, 

 a considerable variation among the individual measures, 

 but no contradictory results. 



Stars having Peculiar Spectra : New V.4Riable Stars. 

 — Harvard College Observatory Circular, No. 143, contains 

 a list of seven stars exhibiting peculiar spectra, and twenty- 

 eight stars shown to be variable. For each star the posi- 

 tion, for looo-o, is given, and the class of spectrum in- 

 dicated, whilst a series of notes summarises the observa- 

 tions. Some of the variables show a long range of magni- 

 tude, in one case amounting to 50. 



Circular No. 151 is a similar publication announcing the 

 discovery of twenty new variable stars in the Harvard 

 map No. 49. It also describes a star in Taurus, at 



R.A. = 5h. 43m. 12s., dec. = 4- 19° 20', 



w'hich varies more than five magnitudes, and exhibits a 

 light-curve of the rare R Coronse Borealis type. Long 

 periods of normal brightness are followed by sudden 

 diminutions over a wide range, the normal brightness being 

 IO-2 and the minimum fainter than 15-5. 



The Natal Government Observatory. — Mr. Nevill's 

 report for the year 1908 deals chiefly with the meteor- 

 ological observations, which, with the time service, form 

 the chief work of the observatory, but it is noted that the 

 large equatorial telescope was overhauled and repaired, and 

 some observations were made with it by Mr. Hodgson. 

 Among these was a new series of lunar photographs, for 

 the determination of the real libration, and some sketches 

 of the surface configurations of Mars, Jupiter, and Saturn. 



NO. 20S7, VOL. 81] 



FIRST MAGNETIC RESULTS OBTAINED ON 



THE -CARNEGIE" IN THE NORTH 



ATLANTIC. 



'T'HE non-magnetic yacht the Carnegie, engaged in a 

 -^ magnetic survey of the oceans under the direction of 

 the Department of Research in Terrestrial Magnetism of 

 the Carnegie Institution of Washington, left Brooklyn, 

 New York, on her first cruise, August 21, and proceeded 

 direct to Gardiner's Bay, Long Island. Here several com- 

 plete swings of the vessel were made with both helms in 

 order to test the instruments, train the observers, and, 

 above all, to determine whether actual non-magnetic con- 

 ditions had been secured at the various positions of the 

 instruments. These tests resulted most satisfactorily, not 

 only proving the absence of deviations in the three mag- 

 netic elements (declination, dip, and intensity), within the 

 errors of observation, at all observation positions, but also 

 showing that with the instruments installed and the 

 methods of observation employed a high degree of accuracy 

 can be obtained. 



Summary of Swi)igs at Gardiner's Bay, Long Island, 

 New York, August 31 to September 2, igog. 



Only one who has had experience both in the observa- 

 tions and reductions of magnetic elements determined at 

 sea can appreciate the full significance of these results and 

 can realise the advance made. 



The above diagram will assist in the interpt-etation of 

 the figures given in the above table, and at the same time 

 make clear the general arrangements of the various instru- 

 ments and the methods used. Consider the plane ABCD 

 to be a vertical section through the four instrument posi- 

 tions and the fore and aft line of the vessel. Position A 

 is on the bridge above the deck or chart-house, B is in the 

 forward observatory, C in the after observatory, and D 

 at the middle point of the chart-house, vertically below A. 

 The sides of the parallelogram are about 135 feet. 



At A is mounted the standard coinpass, one of a new- 

 type invented and constructed by the Departtuent of 

 Terrestrial Magnetism, and called the " marine coUimating 

 compass"; it will be found described in the March (1909) 

 issue of the journal Terrestrial Magnetism. The basis of 



