Februaky 1, 1899.] 



KNOWLEDGE. 



39 



61 CYGNI. 

 To the Editors of Knowledge. 



SiBs, — Dr. Herman Davis's results as regards the 

 parallax of 61 Cygni, mentioned iu your last, strike me as 

 extremely improbable. That, if he is right, the two stars 

 do not form a physical system may be conceded, but, it is 

 to be added, that they do not possess common proper 

 motions. Bring 01- as near to us as 61', and, according 

 to Dr. Davis, the proper motion of the former will be 6-4", 

 and that of the latter 5-!2" per annum. But when we 

 remember how very few stars possess as large a proper motion 

 as either, the chance of finding two such stars (not physi- 

 cally connected) as close to each other as this pair would 

 seem to be very small indeed. And in addition to this we 

 are compelled to suppose that not only are these two stars 

 moving in almost the same direction on the celestial sphere, 

 but that their velocities are almost proportional to their 

 distances from us, so as to produce an apparent common 

 proper motion where one is really moving much faster than 

 the other. A further coincidence is that both stars are nearly 

 alike both in magnitude and colour. Mr. Gore has pointed 

 out that when double stars are nearly equal in magnitude 

 their colour is almost always the same, while if the magni- 

 tudes dififer considerably the colour is different also. It is 

 strange that such a law should be verified in a case where 

 the equality of magnitudes merely results from the greater 

 distance of the star that is really the brighter of the pair. 



We could frame hypotheses according to which almost 

 any of our binary stars would have no physical connection. 

 The companion of Sirius, for example, might be much 

 more distant than the bright star, and be revolving round 

 a dark body, or else round a bright body which was lost in 

 the glare of Sirius. But such hypotheses are out of place 

 in science. 



I hope an effort will be made to measure the velocity of 

 the two stars in question in the line of sight. If they are 

 not physically connected it will probably be different in each 

 case ; otherwise we may expect it to be nearly the same. 



W. H. S. MoNCK. 



THE NOVEMBER METEORS IN 1898. 



OBSERVATIONS of the meteoric shower of No- 

 vember 13th, 1897, were made at the Harvard 

 CoUege Observatory, and a description of the 

 results will be found in the Annals, Vol. XLI., 

 No. 5, and in Circular No. 31. More extensive 

 observations were made in 1898, and the results will 

 be published later in the Annals. Several investigations 

 were undertaken, and some of the preliminary results 

 are given below. As proposed in Circular No. 31, stations 

 have been selected all round the earth in order that 

 counts of the number of meteors visible might be made 

 during the entire time that the earth trav.ersed the 

 meteor stream. The density of different portions of the 

 stream would thus be determined. Reports from the 

 distant stations will not be received for some time. The 

 night of November 13th was cloudy in Cambridge, but 

 on November 11th, eight hundred meteors, not including 

 duplicates, were recorded at this observatory by thirty 

 persons. The maximum occurred at three o'clock in the 

 morning, when sixty-one meteors east of the meridian 

 were counted in half an hour. Two hundred and twenty- 

 seven trails of eighty different meteors, within thirty 

 degrees of the radiant point, were charted. Similar 

 observations were made at Providence by Prof. Upton, 

 of the Ladd Observatory, aided by a number of students. 

 The vicinity of the radiant was watched continuously 



by at least ten observers, who recorded four hundred 

 meteors. This station is forty miles south of Cambridge, 

 and was selected as suitable for determining the parallax 

 visually. Xinety-six photographs were taken at Cam- 

 bridge with the Draper telescopes and with eleven smaller 

 instruments. Five photographic doublets were mounted 

 equatorially and photographed the region within thirty 

 degrees of the radiant, during nearly the entire night. 

 Two cameras were carried to Tufts College, two miles 

 north of Cambridge, and twenty-five photographs were 

 taken simultaneously at both stations for a photographic 

 determination of the parallax. In all, thirty-one trails 

 of eight different meteors were photographed, of which 

 three appeared on one plate. Four meteors were photo- 

 graphed at both stations, and can be used for determining 

 the parallax photographically. The changing distance 

 of the meteors is obvious by inspection of these photo- 

 graphs. A preliminary determination of the radiant was 

 made by prolonging the trails of four meteors. They 

 nearly intersect in a point, the greatest deviation not 

 exceeding one millimetre, or ten minutes. The position 

 of the radiant reduced to 1900 is thus given as R.A.= 

 lOh. CBm., Dec. = 4-22° 16', which is 9m. following, 

 and 38' south of the place given by Denning. Seven- 

 teen plates were taken with prisms, but they failed to 

 show the spectra of any meteors. It appears from the 

 photographs that the light of the meteors attained a maxi- 

 mum and then diminished as rapidly as it increased. 

 In some cases, sudden changes due to explosions are well 

 shown. The trail is sometimes surrounded by a sheath 

 of light, and in one case the trail remaining after the 

 meteor had passed was photographed. These results 

 show that meteoric showers m-iynow be studied to advan- 

 tage by photography. 



November 19th. 1898. Edward C. Pickering. 



PHOTOGRAPH OF THE NEBULA N. G. C. 

 NO. 1499 PERSEI. 



By Isaac Roberts, d.sc, f.r.s. 



THE photograph covers the region between R.A. 

 3h. IBm. 581s. and R.A. 3h. 59m. 'i-23.; declina- 

 tion between 35° 32 4' and 37^ oC north. Scale- 

 one millimetre to thirty seconds of arc. 



Co-ordinates of the fiducial stars marked with 

 dots for the epoch a d. 1900. 



Star ( I D 31. No. 792 Zone +36o E.A. 3h. 5Im. 3-63. Dec. 36° II-9' Mag. 7-0 

 (,.) „ 805 „. +Mo „ 3h. Mm. .39-2s. „ 36" iSfi' „ 7-5 



The photograph was taken with the twenty-inch reflector 

 on 1807, December 18th, between sidereal time 2h. 14m. 

 and 4h. 14m., with an exposure of the plate during ninety 

 minutes. 



Dr. Scheiner, in the Astr. Nach., Band 132, No. 3157, 

 pp. 203-206, gives some particulars, accompanied by a 

 sketch, of this nebula. 



Sir William Herschel, in the Phil. Trans, for the year 

 1811, notes the existence of fifty-two areas in the sky which 

 he believed to be affected with nebulosity. Eight of those 

 areas have already been photographed at my observatory, 

 with the result that upon six of them no nebulosity has 

 been found; therefore we are justified in inferring that 

 upon these areas none exists of brighter luminosity than 

 that of stars of the seventeenth magnitude ; but upon the 

 other two, dense nebulosity has been photographed. 



The photograph annexed hereto is presented upon a 

 scale that will enable astronomers to appreciate the extent, 

 the structural details, and the stars down to the seventeenth 

 magnitude that are apparently involved in the nebulosity, 



