Dec. 6, 1877] 



NA TURE 



105 



The "meteoric fire-ball," as Prof. Coffin calls it, was 

 first seen moving in an easterly direction from a point 

 nearly over the western shore of Lake Michigan, though 

 it may have become luminous somewhat further to the 

 west as the sky was clouded over that region. From 

 thence it was watched until it disappeared out at sea in a 

 south-easterly direction from the island of Nantucket. 

 Its course was therefore about 1,300 miles, and it was 

 seen for several hundred miles on either side of this 

 track. Upwards of 230 descriptions of the meteor were 

 collected, and upon the best of these Prof Coffin under- 

 took the determination of the orbit, by an elaborate pro- 

 cess detailed in his memoir, which formed No. 221 of the 

 " Sm thsonian Contributions to Knowledge," entitled " On 

 the Orbit and Phenomena of a Meteoric Fire-ball, seen 

 July 20, i860." The various accounts of the meteor are 

 printed in the memoir, and reveal some peculiar points of 

 interest in its path. There were two "remarkable ruptures 

 of the main body of the meteor," particularly near the 

 meridian of 77" west of Greenwich, when it separated into 

 two parts nearly equal in size which disappeared below 

 the horizon, as one observer describes it, like a chain- 

 shot. 



Considering that whatever might have been the orbit 

 of the meteor before it became visible, its course while it 

 was under observation, from being so near the earth, must 

 have been controlled almost wholly by her attraction. 

 Prof. Coffin mentions that the orbit he has investigated is 

 not the path of the meteor in space, but the orbit relative 

 to the earth, having the centre of our globe in one of its foci. 

 Approximate elements having been obtained, azimuths and 

 altitudes deduced from them were compared with those 

 given by the various observations to ascertain what modi- 

 fications of the elements were required in order to satisfy 

 them. It was found that with certain corrections thus 

 indicated the first orbit represented tolerably well most 

 of the reliable observations to the west of 76" or 77°, near 

 which the most easterly of the two points from which it 

 was determined, was situated ; but further to the east the 

 discrepancies between calculation and observation were 

 "so great that they could be reconciled only by introducing 

 changes in the elements of the orbit, one on the meridian 

 of 77° and another near the meridian of 74°, ancj as Prof, 

 Coffin remarks, it is worthy of note that it was in the 

 vicinity of these points that observers report the violent 

 ruptures of the body of the meteor, which seems to afford 

 a rational explanation of the changes of elements found 

 to be required. It was apparent that while the meteor 

 descended rapidly towards the earth till it reached the 

 meridian of about 74°, it afterwards rose, and the change 

 was too great to be accounted for on the supposition that 

 the meteor at that point attained the perigee of its hyper- 

 bolic orbit. After the introduction of other considera- 

 tions, it resulted that the path divided itself into three 

 sections, '* the first and third of indefinite length, over 

 only a small portion of which the meteor was visible, and 

 the second an intermediate one, 160 miles long, where it 

 was must brilliant." The elements for the three sections, as 

 finally adopted, are : — 



Sec. I. Sec. II. Sec. III. 



Long, of perigee 294 57 ... 275 37 ... 201 2 



,, descending node... 332 56 ... 325 il ... 329 24 



Inclination to ecliptic 66 12 ... 67 ID ... 66 26 



Eccentricity 29984 ... 2-9817 ... 2 9921 



Major semi-axis 2005-3 ... 2005"3 ... 2005-3 



Perigeal dibtance 4007 ... 3974 ... 3995 



The major semi-axis and the perigeal distances are ex- 

 pressed in miles. According to these elements. Prof. 

 Coffin concludes that the meteor entered the sphere of 

 the earth's attraction from the direction of the constella- 

 tion Sextans, in about R.A. 148°, N.P.D. 87°, and left it 

 toward a point in R.A. 355°, N.P.D. 121°. 



The Planet Mars and B.AC. 8129. — The near ap- 

 proach of Mars to the seventh-magnitude-star, B.A.C. 



8129, appears to have been observed pretty generally. 

 Taking the^mean place of the star from the Washington 

 Catalogue of i860, its apparent position on the evening 

 of November 12 is found to be R.A. 23h. 14m. 24-375., 

 N.P.D. 96° 34' 22 '-5. By Leverrier's tables the place of 

 Mars at 6h. Greenwich time and the hourly motions 

 were : — 



RA 23h. 1400. 24S-9I -i- 3S-473/?. 



N.P.D 96° 34' 25" -I - 30" -49/. 



Taking account of parallax, the star at 6h. would be on 

 an angle of 3i9''-4, distant from planet's centre, i7"-8, b/ 

 calculation, as seen at Greenwich. Probably the actual 

 approach was not quite so close. 



The Binary-star Castor.— Dr. Doberck, of Col. 

 Cooper's Observatory, Markree, whose investis^ations 

 relating to the orbits of the revolving double-stars have 

 been on several occasions referred to in this column, has 

 corrected the elements of the fine binary a Geminorum, 

 given by Thiele in 1859, by measures to 1877 inclusive. 

 Thiele's period of revolution was 997 years, Dr. Doberck's 

 calculation gives 1,001 years, and the comparison with 

 observations, from those of Bradley and Pound in 17 19 to 

 the present year, exhibits no larger differences than are 

 to be attributed to unavoidable errors, or in one or two 

 cases, bias on the part of the observer. The new elements 

 are as follow : — 



Passage of the peri-astre 



174975 



Node 



Node to peri-astre on orbit 



Inclination 



Eccentricity 



Semi-axis major 



Revolution 



27 46 (meridian of 1850). 

 297 13 



44 33 

 03292 



7"-43 

 1001-21 years. 



This orbit gives, for 1878-0, position 234°-9, distance 

 5"76. 



Transits of the Shadow of Titan across the 

 Disc of Saturn. — Mr. Marth has drawn attention to 

 the following dates of transit of the great satellite's 

 shadow, as the only opportunities for obser-zation uniil 

 the year 1891 : — December 9, about 6^h. Greenwich time, 

 December 25, about 5fh., and January 10, about 5h. 



The "Nautical Almanac," 1881. — As usual the 

 Nautical Almanac was published in November, the last 

 volume being for the year 1881, which does not appear to 

 be one distinguished by any particular astronomical 

 phenomena. The two solar eclipses on May 27 and 

 November 21, the first partial, the second annular, aie 

 both invisible in this country, and the line of annularity 

 in the November eclipse runs at great south latitude. 

 The total eclipse of the moon on June 11 will also be 

 invisible here, while in the partial eclipse on December 3 

 (magnitude 0-97) the moon will rise at Greenwich aboui 

 twenty minutes after first contact with the shadow. A 

 transit of Mercury on November 7, will be wholly in- 

 visible in this country, the first external contact (geo- 

 centric) taking place at loh. i6m. 13s., and the last at 

 I5h. 37m. 41S. mean times at Greenwich. The list of 

 visible occultations does not contain any planet, nor any 

 star over the third magnitude. The list of standard stars 

 is on the same scale as for the year 1880, and numbers 

 close upon 200. The Naulical Almanac circ\i\a.tes to the 

 extent of more than 20,000 copies, inclusive of the number 

 appropriated for the use of the Royal Navy. 



OLE RUMER 



WHEN Newton's "Principia" raised the theory of 

 astronomy to a height not previously dreamt of, 

 practical a-^tronomy was still where Tycho Brahe left it 

 almost a century before. Such was the respect paid to 



