I 12 



NA TURE 



IJttnc 3, 1880 



pithectis ludio), an African Lriish-tailed Porcupine (Ath.erura 

 africana) from West Africa, three Indian Tantali {Tantalus 

 Imcocephalus) from India, an American Bison [Bison amirkamcs) 

 from North America, a Schomburgk's Deer (Cervus schom- 

 hurgki) from Siam, two Side-striped Jackals {Cam's laUralis) 

 from West Africa, two Spotted Hyrenas {Hyana crocula) from 

 South Africa, two Cretted Screamers {Chauna chavaria) from 

 Buenos Ayres, five Black-necked Swans {Cygnus nigricolHs) 

 from Antarctic America, purchased; an Axis Deer {Cervus axis), 

 born in the Gardens. 



OUR ASTRONOMICAL COLUMN 

 OccuLTATioN OF A FiXED STAR BY SATURN. — It is recorded 

 by Whiston, in his life of Dr. Clarke, that the father of the 

 latter once saw a star in the dark space Ijetween the ring and the 

 ball, though, so far as we are aware, no date for the observation 

 or other particulars have been preserved. Gottfried Kirch, the 

 discoverer of the great comet of 1680, appears to have been very 

 nearly a witness of a similar phenomenon, if indeed his telescope 

 had been equal to the occasion. Observing Saturn at Leipsicon 

 the evening of January 16, 1679, he remarked, about loh., that 

 the star Tauri of Bayer (114 Tauri Fl.), of the sixth magnitude, 

 was distant only one diameter from the extremity of the ring. 

 The night was changeable, and clouds subsequently interfered, 

 but two hours after midnight he found the star " quarta forsan 

 parte diametri Saturni, a Saturno distantem." A quarter of an 

 hour later he saw that the distance had sensibly diminished, and 

 in another half hour the star had become so small "adeo ut 

 ferme eonspectum fugeret. Neque procul aberat a Saturno, ut 

 spatium inter Saturnum et stellulam, ipsius stelk-e magnitudinem 

 non superare videretur;" and he continues: " SteUula postea 

 tangebat ferine extremum Saturni.'' An accompanying rough 

 figure shows the star very nearly in contact with the ex- 

 tremity of the ring. Further we read: "Inter primum et 

 secundum quadrantem po^t horam tertiam nihil dignoscere 

 poteram, primo slellula Saturno adhresisse mihi videbatur, 

 de quo tamen nihil certi dicere possum, ipse enim dubito; 

 delude nihil videndum sese oflerabat." But although he saw 

 no more, Kircli states that Saturn would necessarily shortly 

 occult the star. On the following evening, at Sh. 30m., the 

 star was distant about a diameter of the planet, or rather, as 

 the figure shows, of the ring. He considered from these obser- 

 vations that the star was in contact at 3 a.m. on Januai-y 17, and 

 that the egress took place about 11 a.m. It will be found that 

 Saturn did not set at Leipsic on thii morning until nearly 

 5h. 30m., and by the track of the planet the central distance at 

 conjunction was less than a third of the semi-diameter of the 

 shorter axis of the ring, thus the star might be within the dark space 

 between the ring and the globe before setting. The planet was 

 then about 83° from the node of the ring, which must therefore 

 have been nearly as open as we can see it. Kirch seems to have 

 been well aware of the rarity of such an obiervation. It w as 

 first published in his Ephemerides for 16S3. 



The^ Polar Compression of Mars.— In November last 

 Prof. Young made a numerous series of measures of the dia- 

 meters of Mars with a filar-micrometer attached to the 9'5-inch 

 equatorial of the School of Science Observatoi7 at Princeton, 

 New Jersey, U.S., the object-gla-s of which is stated to be of 

 the highest excellence, having repeatedly shown both satellites 

 of Mars, the two outer satellites of Uranus, and, it is said, the 

 Saturman satellite Mimas. Although measures with the wire- 

 micrometer have been found liable to considerable constant error. 

 It was thought they might safely be used in determining a differ- 

 ence of diameter. Mr. Marth's ephemeris was employed in 

 setting the position-circle and in computing the minute correc- 

 tions for phase. The total number of micrometer-readings was 

 1,140. The results applicable to November 12, 1S79, are as 

 follow : — 



Equatorial diameter 

 Polar diameter 

 Mean 



.. 20-634 ± 0034 

 .. 20-552 ± 0-043 

 .. 20-593 ± 0-035 

 These absolute values Prof. Young considered not very re- 

 liable, being subject to the considerable constant error referred 

 to above. 



Dr. Hartwig's determination of the mean diameter of Mar.s, 

 by combining all the double-image measures at Konigsberg, 



Leyden, Oxford, Berlin, Paris, and Strassburg, gives for the 

 opposition-diameter in 1879, I9"-I2S, which differs from Prof. 

 Yoimg's result by l"-46, which he says is a difference "rather 

 unexpectedly large, but not unprecedented." As regards the 

 compression, the immediate object of the Princeton measure--, 

 the final result comes out -j},-, the limits of probable error ex- 

 tending from y^iT to •^. The discussion of the measures 

 was nearly finished, when Prof. J. C. Adams's paper upon the 

 orbits of the satellites of Mars was published ; he there gives 

 TTj-j as the ellipticity of the planet, if it follows the same law of 

 central density as the earth. This near agi-eement is probably 

 to a considerable extent an accidental one. 



Dr. Hartwig's value for the polar diameter of Mars at distance 

 unity is 9"-352, corresponding, with Leverrier's solar parallax, 

 to a real diameter of 4,180 miles. 



The Next Total Solar Eclipse. — At the recent annual 

 meeting of the National Academy of Sciences at Washington, 

 Mr. D. P. Todd, of the office of the American Ephemeris, com- 

 municated a paper "On the Use of the Electric Telegraph 

 during Total Eclipses applied to the Search for Intra-JIercurial 

 Planets," with the view to illustrate in what manner the 

 rare moments of total eclipses may be utilised to their utmost 

 extent, " the method consisting in the electro-telegraphic trans- 

 mission of important observations made at western stations to 

 observers at eastern stations, with due speed for their verification 

 or rejection when the lunar shadow reaches the latter stations." 

 Taking as an example tlie next total eclipse of the sun, on May 

 16, 1882, it is remarked that the path of totality lies almost 

 wholly on land ; commencing in Western Africa, with a north- 

 easterly direction, it crosses Upper Egypt and the Red Sea, 

 passing a few miles south of Bagdad and Teheran, and thence 

 traversing Central Asia, it leaves that continent near Shanghai. 

 Thus several widely-separated regions, connected by telegraphic 

 cables and land lines, are up3n the track of the central eclipse. 

 Mr. Todd remarks that from El-Akhmym, on the Nile, a line 

 runs north to Alexandria, from which place Teheran is directly 

 accessible by telegraph. From Teheran a land-line runs south- 

 cast through Beluchistan and Hindostan to Madras, w'hich is 

 connected by cable-lines with Singapore, Hong-kong, and 

 Shanghai. He points out that an additional advantage attaches 

 to this eclipse from the circumstance that there is a duplicate line 

 of telegraphic connection bet\\een Egypt and Shanghai by way 

 of Constantinople, Vienna, and Moscow, and thence by the 

 Russian line through Siberia to Wladiwostok, and thence to 

 Sh.anghai. Supposing, then, that an intra-Mercurial planet were 

 discovered during totality in Egypt, a duplicate message might be 

 sent, to insure beyond doubt tliat the discovery should be known 

 to observers at .Shanghai ; if a planet were observed at El- 

 Akhmym, 45 minutes of absolute time elapsing before the shadow 

 reaches Telieran, the position might be telegraphed to the latter 

 station so as to give the observer abundant time to verify the 

 discovery, while observations at both places might be telegraphed 

 to Shanghai, which the shadow will not reach until more than 

 two hours after leaving Teheran. Mr. Todd thinks that the 

 telegraph companies, with the conrtesy they have always shown 

 in scientific undertakings, would render every assistance in 

 carrying out such a scheme. 



We take this outline from a report 'of his communication to 

 the American Academy, received from Mr, Todd. 



BIOLOGICAL NOTES 



Chinese Alligators. —Two fine examples of the alligator 

 of the Yang-tse-kiang, of the discovery of which we spoke in 

 our issue of February 13, 1879 (vol. xix. p. 351), have recently 

 been received by Dr. Peters for the Zoological Museum of Ber- 

 lin. There can be no doubt, we understand, that M. Fauvel 

 is quite right, and that this crocodilian is an undoubted alli- 

 galor — being the first of this genus which has been found to 

 occur in the Old World. It will be recollected that of the 

 remarkable Chondrostean genus of fishes, Polyodon, one of the 

 two known species is also found in the Yang-tse, while the 

 other is confined to the Mississippi. 



Fossil Corals. —The Cyathocrinids, as one of the largest and 

 most ancient groups of fossils, appear to belong to a type worthy of 

 attracting continual study. Wachsmuth and Springer {Proc. Acad. 

 Nat. Sci., Philad., 1S79) unite the genera Poterlocrinus and Cya- 

 thocrinus into one family, finding them agreeing in having large 

 oral plates supporting the ambulacral grooves and covering the 



