454 



NATURE 



[February 2, J911 



iiut Mr. Worssell found it visible — and probably variable — 

 in 1909-10, its iiiagnitude ranging from ii-o (1909 July 21) 

 to \2-2 (1909 September 5). This star lies on the border 

 of the abnormally tinted patch of the sky, and it is 

 suggested that its disappearance in 1899-1901 may have 

 ijeen due to a slight extension of the obscuring medium, 

 which is now retreating. 



Photographic Determinations of Stellar Parallax. — 

 To No. 5, vol. xxxii., of the Astrophysical Journal Prof. 

 F. Schlesinger contributes the first part of a paper on the 

 photographic determinations of stellar parallax made with 

 the Yerkes refractor. Previous parallax determinations 

 have usually been made with short-focus instruments, and 

 it occurred to Prof. Schlesinger, in 1902, that the errors 

 ■of observation might be greatly reduced if much greater 

 focal lengths were employed ; the cooperation of the Yerkes 

 authorities and the Carnegie Institution rendered this 

 possible, and 327 plates, relating to twenty-five different 

 regions, were secured, and have been reduced for the 

 purposes of the present papers. 



In this first paper Dr. Schlesinger describes in detail 

 the apparatus and methods employed in securing the 

 photographs. The question of using screens, for the 

 sharpening of the stellar images, was considered, but it 

 was decided not to use them, as difficulties might be intro- 

 ■duced ; also, it was found that, with the 40-inch objective 

 used with Cramer Instantaneous Isochromatic plates, they 

 were really unnecessary. A special movable plate-carrier, 

 adjustable in two directions by means of screws, was 

 employed, and the coincidence of the optical axis and the 

 geometrical centre of the plate was investigated ; it was 

 'found that they were separated on the plate by about 

 '8 cm. (about fourteen minutes of arc), but the final effect 

 was negligible, and, as the radical correction of the tilt 

 would have interfered with other instruments used with 

 the 40-inch, no attempt was made to correct it. The 

 focussing each evening was done visually by means of an 

 ■eye-piece sliding on a graduated scale. The " hour-angle 

 error," produced by atmospheric dispersion, was 

 ■eliminated, so far as possible, by choosing the hour-angle 

 at which each plate was exposed ; it was also deemed 

 advisable to use the telescope on one side of the pillar 

 ■only, in order to eliminate "optical distortion." After 

 several experiments an ingenious " rotating disc " occult- 

 ing shutter was employed for reducing the brightness of 

 the parallax star to that of the surrounding comparison 

 sTars. 



Many other interesting points are discussed bv Dr. 

 "Schlesinger, but space does not permit of their being 

 mentioned here. It may, however, be added that the scale 

 •of the plates is such that i mm. corresponds to 10-6'', and 

 "that 20 cm. X25 cm. plates were used. 



Lines in the Spectra of Nebula. — No 

 "Lick Observatory Bulletins contains 

 •discovered photographically by Dr. 



the great nebula of Orion he finds lines at A 3734 (faint), 

 A 3722 (v. faint), \ 3712 (v.v. faint), and X 3704 (v. faint), 

 all of which he ascribes to hydrogen ; another line is 

 suspected at A. 4137. 



In N.G.C.7027 lines were found at X 6301, X 654.8, and 

 ^ 6583, the latter two making a conspicuous triplet with 

 Ho, which is very bright in all the nebulae that ha%-e been 

 -observed. 



Utilisation of the Sun's Heat. — In the January 

 number of L' Astronomic — to which title the Bulletin de 

 la Societe astronomique de France has reverted — Prof. 

 Ceraski describes and illustrates a very simple thermo- 

 electric pile which he made and which gives sufficient 

 current to ring an electric bell whenever the sun shines. 

 He also suggests, hesitatingly, that if made up in sufficient 

 numbers and placed in suitable localities, batteries of such 

 ■piles might be employed in utilising the solar radiations. 



PROPOSED CALENDAR REFORM. 

 pROPOS.\LS for reformation of the calendar have been 

 somewhat numerous of late years, and few of the 

 proposers appear to have a full sense of how much trouble 

 and inconvenience any alteration would cause, and, of 

 course, the more radical the change is the greater this 



of the 

 1 list of nebula lines 

 W. H. Wright. In 



would be. Mr. T. C. Chamberlin, indeed, who puts forth 

 another scheme in the number of Science for Noveinbp'- 

 25, 1910, admits that it is important that if any alterati- 

 is adopted, its advantages should be so great and 

 unique that no further modification of it would ever appea, 

 desirable. 



Now all the alterations lately proposed, including tl 

 one before us, are of a far more drastic kind than ti 

 Julian and Gregorian reforms, which only aimed .. 

 securing that the monthly and other dates in the calendar 

 should correspond to the season of the year, the whol 

 length of the calendar year being of the same length a- 

 a tropical year. Even in the time of Julius Caesar it wa 

 known that the length of the latter was a few mi nut 

 less than 365^ days. Following the practice of the <>' 

 Egyptians (and guided partly by the advice of Sosigene 

 when he made the Roman calendar wholly solar, he pro 

 ably thought that it would be better, because simpler, 

 take the length of the year as 365^ days, and that I'n 

 would secure the correspondence with the seasons for 

 sufficiently long period. .As time went on, of course, ti 

 difference between this and the true length became mo: 

 accurately known. 



The ecclesiastical authorities, in arranging the cycl 

 for the observance of Easter, considered it essential tha 

 though that feast was movable on account of its beiii.:^ 

 taken as dependent on the Jewish Passover, which wa~ 

 regulated by the moon, yet it was necessary to take thr> 

 moon the full of which followed the vernal equinox, and 

 to give that equinox the date which it had (or was sup- 

 posed to have) at the time of the first great Council of 

 the Church, that of Nicasa. To do this it was necessary, 

 I not only to alter in future the length of the calendar year, 

 but to drop the days, then ten in number, by which th* 

 date of the equinox had changed since the time of thi> 

 Council. 



The Gregorian alteration, then, was introduced in 1582 : 

 but the Reformation of the Church, which had then been 

 accepted in many countries in the north of Europe, led 

 to this change being opposed by them, though it wa 

 ultimately adopted all over western Europe, and cons 

 quently in North America. 



But the changes we are now called upon to discuss an^ 

 of a very different nature. Most of the proposers seem 

 to think there would be very special advantage in makini^ 

 artificial arrangements by which the days of the week 

 should correspond to those of the month, which, of course, 

 could only be effected by making every month 28 days (or 

 4 weeks) in length. Some would increase the number of 

 months in each year to 13, and as 13x28 = 364, suggest 

 that the correspondence might be maintained by treating 

 one day as a dies non, which would have to be made two 

 in leap-years. But it would not be possible to treat a day 

 as dies non in any complete sense. It could, of cours 

 easily be made a holiday, but even in holidays all mi: 

 do something, and manv a great deal. 



The peculiarity of Mr. Chamberlin 's plan seems to be 

 to retain our 12 months, but at the end of each quarter, 

 or period of three months, to insert a week with a special 

 designation, the thirteenth week of the year to be called 

 Easter week, the twenty-sixth Julian week, the thirty- 

 ninth Gregorian week, and the fifty-second Christmas 

 week. The idea seems to be that a week is needed at 

 the end of each quarter for arranging accounts and other 

 matters. 



Having set forth the salient points in this fresh attempt 

 at symmetry in the calendar, we leave it to our readers to • 

 form their opinion about whether changes of this drastic 

 nature would procure advantages comparable with the 

 trouble caused. Many, no doubt, will be reminded of the 

 famous interrogatory of Lord Melbourne. 



The same remark, in the writer's opinion, may be made 

 of another proposal by M. Grosclaude, of Geneva, for 

 which the approval of a congress at Brussels is claimed. 

 According to this, the year would consist of four Quarters, 

 each containing thirteen weeks ; but while the first two 

 months of each quarter would have only thirty days, the 

 third would have thirtv-one. This would give the year 

 364 days ; the remaining dav (two, of course, in leap-year^ 

 would be made up as in Mr. Chamberlln's plan. 



W. T. L. 



NO. 2153, VOL. 85] 



