September 23, 191 5] 



NATURE 



95 



OVR ASTRONOMICAL COLUMN. 

 The Supposed New Comet. — Ephemeris Circu- 

 lar No. 492 of the Astronotnisclie Nachrichten con- 

 tains a notice from Prof H. Kobold, Kiel, announc- 

 ing that Prof. Frost has identified the supposed new 

 comet discovered by Mr. J. E. Mellish on September 6 

 with N.G.C. 2261. 



Star Colours. — There are two methods by which 

 the colours of stars are being determined :— (i) the 

 direct method, in which a coarse objective grating is 

 used, and estimates made of the mean effective wave- 

 lengths of the light from the stars; and (2) compari- 

 son of the relative intensities of two separate regions 

 of the stellar spectrum. As usually effected, this is 

 an indirect method, based on measures of photo- 

 graphic and visual (or photovisual) magnitudes. 

 Three recent contributions from Mount Wilson 

 Observatory, {Astrophysical Journal, vol. xli.. No. i) 

 deal with this subject. In one of these Prof. E. 

 Hertzsprung presents an account of his researches 

 on the stars in the cluster N.G.C. 1647 by 

 the grating method used in conjunction with the 

 6o-in. reflector of the Mount Wilson Observatory. 

 Photometric magnitudes and effective wave-lengths 

 are given for rather more than 200 stars in the 

 cluster. In the case of 44 stars, a comparison of the 

 measures of effective wave-length are compared with 

 a rough classification of the spectrum. Partly from 

 this paper, Mr. F. H. Seares derives data for a com- 

 parative study of colour-indices measured indirectly 

 with those obtained by transforming effective wave- 

 lengths. Results for 47 stars of magnitudes between 

 11-5 and 15 indicate that for this interval the two 

 series of colour-indices show the same, increase in 

 mean colour with increasing magnitude. In the re- 

 maining paper, Prof. Hertzsprung discusses the mean 

 effective wave-length of a number of absolutely faint 

 stars. Effective wave-lengths show lit*;le change for 

 stars of abs. mag. -I- 3 and +8, the values lying 

 between AA 4500-4600. The suggestion is made that 

 the abs. mag. +3, corresponding to a temperature of 

 3400° abs. for a black body the size of the sun, repre- 

 sents the stage of a cooling star at which relatively 

 dark solid matter begins to form on its surface. 



Raies Ultimes. — Comte A. de Gramont designates 

 by this term those lines in the spectrum of an element 

 which for any given source of luminescence persist 

 longest as the percentage of the element is reduced. 

 They are thus lines of maximum sensitivity. In a 

 paper lately published {Ann. Chem., vol. iii., May- 

 June, 1915) it is pointed out that the effect of reduc- 

 tion of quantity of substance should not be confounded 

 with diminished exposure in photographing the 

 spectrum. The one operates on the spectrum, 

 the other acts merely on the record. The 

 persistent lines are not identical in the two 

 cases. It appears that in general the vestigial 

 spectrum is not of necessity made up of remnants 

 of the strongest lines of the elements, though, in fact, 

 the raies ultimes mostly seem to be either the strongest 

 or among the strongest lines, and they are usually 

 lines which readily reverse. They bear some 



irt of relationship to the "long" lines employed by 

 >ir Norman Lockyer some forty years ago as criteria 

 to establish the presence of less spectroscopically con- 

 spicuous elements in the sun. The paper contains 

 interesting suggestions regarding the energy distribu- 

 tion in line sp>ectra and on the relationship between 

 the raies ultimes and the point of maximum radiation. 



Eari.y Nautical Astronomy. — An address on the 

 boginnings of geogfraphical science, delivered by Sir 

 Clements R. Markham before the Royal Geographical 



NO. 2395, VOL. 96] 



Society on June 10 last (Geographical Journal, vol. 

 xlvi., No. 3, September, 1915), contains much ex- 

 tremely interesting information regarding the develop- 

 ment of astronomical methods, instruments and tables, 

 employed in navigation during the period of revival 

 of nautical adventure ; the period of the first Trans- 

 atlantic voyage, and the rounding of the Cape of 

 Good Hope. It was, in fact, the efforts of the Portu- 

 guese to open up the western coast of .\frica, leading 

 seamen into southern waters out of sight of the familiar 

 Polaris, that necessitated the formulation of new 

 methods. A mathematical Junta appointed by King 

 Joao II. of Portugal (1481-95) triumphed over the 

 difficulties. It now appears that a Jewish royal 

 physician was the leading spirit of the commission, 

 and it was a friend of his, Abraham Zacuto, pro- 

 fessor of astronomy at Salamanca, who had ready at 

 hand the requisite tables giving the sun's declination. 

 Lack of space forbids further description here. The 

 lecturer drew largely on the researches of Senhor 

 Joaquim Bensaude, in particular on the latter's work 

 " L'Astronomie nautique au Portugal k I'^poque 

 des grandes d^couvertes," Bern, 1912. 



Approximate Determination of Planetary Longi- 

 tude. — In Knowledge (August) Prof. Herbert Chatley 

 gives a simplified method of calculating planetary 

 longitudes for elliptic orbits without employing intri- 

 cate mathematics. The method depends on the 

 assumption, apparently very nearly true, that the 

 difference between uniform circular motion and 

 elliptic is harmonic. It is claimed that the method 

 is capable of giving results to within a few minutes 

 of arc. 



THE CANADIAN ARCTIC EXPEDITION. 



TyrR. VILJALMUR STEFANSSON, the Canadian 

 ^^^ Arctic explorer, whose unexpected safety is 

 announced, contributes his personal narrative of the 

 expedition to Monday's Daily Chronicle. He left Alaska 

 in July, 1913, for the Beaufort Sea. Bases were also 

 to be established on Prince Albert 'Sound and Patrtck 

 Island. Mr. Stefansson was accompanied by Dr. 

 Forbes Mackayand Mr. James Murray, of Shackle- 

 ton's first Antarctic expedition; M. Henri Beuchat, a 

 French anthropologist, who was "to study the Eskimo 

 of Bank Land; Mr. W. L. McKinlay and others. 

 Captain Bartlett, of Pear>''s North Pole expedition, 

 was in charge of the Karluk, the main ship of the 

 expedition. Whether or not the Karluk could reach 

 Patrick Island and penetrate the Beaufort Sea de- 

 pended on the prevailing winds. With a persistence 

 of easterlies, which Stefansson hoped for, this would 

 be possible, but otherwise he realised that his plans 

 must be modified. 



Earlv in August, 1913, the Karluk was beset in 

 the ice in 147° W., fifteen miles off the shore. In the 

 belief that the ship was firmly frozen in, Stefansson, 

 with three companions, went ashore to hunt towards 

 the end of September. During their absence a strong 

 north-easterly gale broke up the ice and carried the 

 ship awav to the west. Passing near the coast firmly 

 beset in the ice the Karluk was carried north-westward 

 to 73° N. 162° W. on November 11. Her drift then 

 changed to south-west, and by the end of the ygar 

 she was sixty miles north-east of Herald Island. Two 

 weeks later the ship was crushed and sank, but not 

 before a quantity of stores had been placed on the 

 ice. Herald Island could not be approached on 

 account of open water, so tracks were made success- 

 fullv for Wrangell Island. \ party of eight, however, 

 including Dr. Mackav, Mr. Murray, and M. Beuchat, 

 who had left the Karluk earlier in an attempt to reach 



NO. 2395, VOL. 96] 



