374 



NATURE 



[SePTEMUER 22, 19IO 



OVR ASTRONOMICAL COLUMN. 



Further Observations of Halley's Comet. — In 

 Bulletin No. 20 of the Kadaikdnal Observatory Messrs. 

 .Vlichie Smith and John Evershed give an account of the 

 (ibservations of Halley's comet made with various instru- 

 ments during .April and May. A number of photographs, 

 which may fill in the blanks between those taken in 

 .\merica and in Europe, were secured with a 5-inch Grubb 

 portrait lens of 33-8 inches focal length. On certain of 

 these there are many distinct tails and a number of fine 

 details ; other plates were exposed in a half-plate Ross 

 camera giving a scale of i mm. = 17.5'. Mr. Evershed 

 used a 95-inch reflector, of 74 inches focal length, fed by 

 a 16-inch coelostat, and secured a number of photographs 

 showing the intricacies of the structure in the head, the 

 scale being i mm. = 110". 



Spectrograms were also secured, and show the differ- 

 ences between the radiations from the head and those from 

 the tail observed in Daniel's comet iqoyd ; the continuous 

 spectrum of the nucleus shows, faintly, a considerable 

 number of Fraunhoferic lines attributable to reflected sun- 

 light. In the head, the pair of " cyanogen " radiations 

 at X 3871 and \ 3883 appear to account for at least two- 

 thirds of the total emission, and the preliminary examina- 

 lion shows no essential variation in the spectrum between 

 .\pril iq and May 15. In the very strong band at X 4645- 

 4744, five or si.x separate lines can be distinguished on 

 some of the spectrograms. Visual observations showed 

 that the very bright comet lines in the green and blue 

 could be traced a long distance into the tail and to some 

 considerable distance on the other side of the nucleus. 



Notwithstanding the small dispersion (i mm. = 73 A. 

 at 4227), measurable displacements of the cometary lines, as 

 compared with lines in the spectrum of Venus, were found, 

 and on May 2 gave a relative approach of 77 km. per 

 sec, the ephemeris value being 68 km. per sec. ; but to 

 this must be added the recessional velocity of Venus. 



The programme for the detection of the comet during 

 transit was very complete, and is described in detail, but, 

 as has been stated before, no trace was found. 



Observations of the tail were made by Mr. Evershed, 

 u'lio describes its appearance during May 18-21. He 

 suggests that the persistence of the phenomenon in the 

 east may be explained by supposing the tail to have been 

 very broad in the direction of its motion, although 

 relatively narrow in the direction at right angles to this ; 

 with a strong curvature, this would account for the 

 apparent length of time for the earth to make the com- 

 plete passage. 



In the September number of the Bullelin de la Societv 

 astronotniquc de France there are reproduced some excel- 

 lent photographs taken by M. Mascart at Teneriffe, as 

 well as a nuinber of drawings and accounts by various 

 other observers. 



Dr. C. D. Perrine, director of the Observatorio Astro- 

 nomico of the ."Argentine Republic, writing from C6rdoba 

 on August 18, says : — " It will be of interest to your 

 readers to know that we are still observing Halley's comet. 

 It is some 2' or 3' in diameter, of about the ninth magni- 

 cude, with a nucleus of eleventh magnitude. It is getting 

 so low in the west, however, that we will not be able to 

 follow it much longer." 



The Distances of Red Stars. — .Another contribution to 

 the question of the correlation between spectral t\'pe and 

 parallax, in the form of an abstract of a paper read by 

 Dr. H. Norris Russell, appears in No. 195 (vol. xlix.) of 

 the Proceedings of the American Philosophical Society. 

 Dr. Russell compared the parallaxes of stars measured by 

 Mr. Hinks and himself at Cambridge with the spectral 

 ivpes determined at Harvard, and found that the percentage 

 of orange and red stars increases steadily as the distance 

 from our system decreases. Further, a comparison of the 

 vyijserved parallaxes of stars having large proper motions 

 w'th the parallaxes computed from Kapteyn's formula 

 shows that while the formula stands for the stars of all 

 ( lasses taken together, there are marked deviations when 

 spectra types are considered separately ; the observed 

 parallax of the red stars is nearly twice the computed 

 value. -As all the stars considered are similar in .apparent 

 brightness, it follows that redness is attended bv intrinsic 



faintness, the reddest stars averaging one-fiftieth the 

 brightness of the sun. On the other hand, some bright- 

 red stars, such as .Arcturus and Antares, are known to be 

 at great distances, and are probably at least one hundred 

 times as bright as the sun. 



This conclusion confirms the important hypothesis (now 

 well established on other grounds) that there are two 

 classes of red stars, one class getting hotter, the other 

 cooling. In the intermediate stages the stars would be 

 hotter, passing through orange and yellow to white, and 

 back to red as it approached extinction. 



" Mock Suns " at Eastbourne. — From Mrs. A. M. 

 Butler, of Reigate, we have received further particulars of 

 the " mock suns " phenomena referred to in these columns 

 last week as having been seen at Eastbourne on Sep- 

 tember 10. Mrs. Butler and her daughters watched the 

 phenomena from 12.45 p.m., and saw everything described 

 by Mr. Ronca except the fainter small circle to which the. 

 brilliant chromatic curve was tangential. In addition they 

 saw, to the S.E. of the sun, part of another coloured 

 curve, having its convex side turned towards the actual 

 sun. From an effective coloured sketch of the pheno- 

 mena, drawn by Mrs. Butler, it would appear that this 

 second curve, which was seen at 1.20 p.m., was of about 

 the same radius as the former, and would have barely 

 intersected it had both been continued. 



.Astronomy in India. — From the Pioneer Mail of 

 August 26 we are pleased to learn that an association for 

 the promotion of astronomy has been formed in India. It 

 is to be known as the Astronomical Society of India, and 

 has its headquarters at Calcutta. 



The special objects of the society will be to assist 

 observers by holding meetings, whereat papers will be read 

 and discussed, and by disseminating astronomical news. 

 It is proposed also to found a library of astronomical 

 literature and to publish a journal for each month of the 

 session.- The president is Mr. H. G. Tompkins, Treasury 

 Buildings, Calcutta, to whom all communications should 

 be addressed. 



THE CRUSADE AGAL\'ST CONSUMPTION. 

 17 OR many years the National Association for the Pre- 

 vention of Consumption worked away unostentatiously 

 but pertinaciously. The experience gained during these 

 vears must now be to them of great value in the educa- 

 tional crusade they have undertaken. During the past year 

 an educational exhibition has been going the round of 

 London, into the provinces, east and west and north, to 

 Oxford, Cambridge, Liverpool, Edinburgh, &c. Nothing 

 has been more gratifying or more promising for the 

 ultimate success of this crusade than the keen interest that 

 has been taken in this exhibition, and in the lectures and 

 conferences by all sorts and conditions of men — and 

 women, too, for that matter. We should, naturally, expect 

 public health authorities to be interested, but all who have 

 seen the audiences gathered together at these lectures and 

 conferences cannot but have been impressed by the in- 

 telligent interest taken, even by the very poor, in the 

 question of the prevention of the spread of tuberculosis. 

 Some of the work undertaken by the association at one 

 time appeared to come dangerously near interfering with 

 or overlapping the work of the local medical authorities, 

 and with hospitals and associations already in existence ; 

 but through the good sense of those who, though working 

 in different directions, are mutually interested in putting a 

 check on the spread of consumption, the danger of such 

 overlapping is gradually being minimised. 



The class amongst which tuberculosis is most prevalent, 

 the badly housed and badly fed, has, up to the present, and 

 very naturally, entertained a suspicion that those who 

 looked upon tuberculosis as an infective disease might 

 interfere too much with the liberty of the tuberculous 

 worker, and by isolating him deprive him of his means of 

 subsistence. Nowhere has the educational campaign done 

 better work than in bringing home to these people the 

 immense importance of observing certain fundamental 

 principles of hygiene, not only in their -own immediate 

 interest, but in the interests of those with whom they are 

 most closely associated. It is now well known what pre- 



NO. 2134, VOL. 84] 



