292 



NATURE 



{Atig. 12, 1875 



steep, is positive proof that the non-existence of extensive reefs 

 cannot in such places be owing to any deleterious influences 

 arising from volcanic action, but must be on account of the 

 depth of water on the coast. S. J. Whitmee 



Vpolu, Samoa 



Mirage on Snowdon 



On Monday, July 12, I, with a party, ascended Snowdon. The 

 atmosphere was clear until we had reached within half a mile of 

 the summit, when a light cloud rising stealthily from amongst the 

 southern peaks enveloped it. Drifting towards us, when very near, 

 the cloud dropped over the eastern shoulder of the mountain just 

 where it dips towards Capel Curig. As we stood watching, great 

 was our surprise and delight as we beheld painted upon it, not 

 the arc-en-ciel with which we are familiar, but a complete and 

 brilliant prismatic circle, apparently about thirty feet in diameter, 

 in the very centre of which we ourselves were depicted, the 

 image being somewhat enlarged but clearly defined ; as we 

 arranged the party in groups, or bowed to each other, every 

 form and movement was faithfully reproduced in the picture. It 

 was now about 8 o'clock, with the sun nearly in a line with us. 

 Our guide, who had made some hundreds of ascents, had never 

 witnessed such a sight before, H. J. Wetenhall 



Fordfield, Cambridge 



OUR ASTRONOMICAL COLUMN 



Kepler's Nova, 1604. — We learn from Prof. Winnecke 

 that, in consequence of the remarks upon this star which 

 appeared in Nature, vol. xi. p. 249, he has lately 

 examined the neighbourhood, and, in addition to the star 

 of ii"i2th magnitude there mentioned — the position of 

 which for 185 5*0 he finds to be R.A. lyh. 22m. 4"6s., 

 N.P.D. 111° 23'6'— he found one of 12th magnitude in 

 R.A. lyh. 2im. 49'3s., N.P.D. 111° 19-3'. This star agrees 

 almost precisely in place with the loth magnitude marked 

 upon No. 52 of Chacornac's charts, though not at present 

 of that brightness ; but we are able to state that in August 

 1871 and June 1872 nothing was visible in this position in 

 a telescope which would show stars to I3"i4 magnitude 

 in Winnecke's scale. It will be desirable to watch this 

 small star closely, as it is quite possible it might be 

 identical with Kepler's famous star, the observed place of 

 which is not so accurately known as in the case of the 

 similar object observed by Tycho Brahe in 1572. Prof. 

 Winnecke, however, suggests that, as the star marked by 

 Chacornac is just upon the margin of his map, where 

 some distortion exists, it might possibly be identical 

 with No. 16,872 of Oeltzen's Argelander, a star estimated 

 8*9 in the Bonn Zones ; still the place of the 12th magni- 

 tude agrees much more closely with that of Chacornac's 

 loth, read off from his chart as nearly as the circumstances 

 permit. It may be well to compare the fainter star found 

 by Prof. Winnecke, from time to time with the 11 •12th 

 close at hand, and easily identified if the instrument be 

 set for Argelander's star, which may be considered a bright 

 9th magnitude. 



The Binary Star 4 Aquarii. — If good measures of 

 this star are practicable during the present season, an 

 idea of the form of the orbit may perhaps be obtained. 

 Dawes's series of epochs will be of material service in 

 this respect ; without them, doubt might have been occa- 

 sioned by the two discordant epochs of Madler, which 

 may have been owing to distorted images at low altitude. 

 The object is certainly one of considerable difficulty, and 

 really trustworthy measures are perhaps only to be ex- 

 pected from practised observers in command of instru- 

 ments of excellent definition. In Barclay's second cata- 

 logue it is described as just elongated in the direction 

 144°, with power 450 on the lo-inch refractor at Leyton, 

 at the epoch 186574; this angle shows direct progress, 

 ver}' much in accordance with Dawes's measures. Pos- 

 sibly the companion may now be found nearly due south 

 of the primary. 



The Nebula. — Prof. Schonfeld has published in Part 

 II. of " Astronomische Beobachtungen zu Mannheim" — 

 Carlsruhe, 1875 — a continuation of the valuable series of 

 observations commenced by him in i860, for accurate 

 determination of the positions of a selected hst of nebulas. 

 In this second part we have the places of 336 of these 

 objects, obtained by direct reference to stars, which, as in 

 the case of those employed in fixing the positions of the 

 nebulae included in the first part (Mannheim, 1862), have 

 been meridionally determined at Bonn by the late Prof. 

 Argelander ; the mean places are found in Vol. vi. of the 

 Bonn Observations. Schonfeld's epoch is as before, 

 1 865-0, for which year the precessions are computed with 

 Bessel's constants, still preferred by many of the German 

 astronomers. The differences from Schultz's Preliminary 

 Catalogue are shown, and are generally small. As one 

 result of more recent observations, it is remarked by 

 Schonfeld that a sensible proper motion of the great 

 nebula in Andromedas, which appeared to be indicated 

 by a comparison of Flamsteed's observations with those 

 of D'Agelet and Lalande, is not confirmed. 



Prof. Adams, in his last address as President of the 

 Royal Astronomical Society, remarks upon the great 

 value attaching to Schonfeld's micrometrical observations 

 of the nebulcc, of which we have here the continuation. 



Encke's Comet. — Mr. J. Tebbutt of Windsor, New 

 South Wales, reports his discovery of a comet, which he 

 supposed to be Encke's, on the morning of May 7th, in 

 the constellation Cetus. It is, we believe, the second 

 occasion upon which this able amateur astronomer has 

 detected this comet, before the arrival of an ephemeris 

 from Europe, and no doubt in the present case his inde- 

 pendent discovery, which he communicated telegraphi- 

 cally to the Government astronomers at Sydney and 

 Melbourne, will lead to a number of observations for 

 position at the Australian observatories, which might have 

 been otherwise lost. The search for comets without the 

 aid of an ephemeris is hardly an occupation which can be 

 expected in a public observatory, where time is valuable 

 for routine work — hence an argument for the early and 

 general pubhcation of ephemendes — and an inducement 

 for some amateurs, especially in southern latitudes where 

 a great necessity for systematic sweeping of the sky in 

 search of comets appears still to exist, to so employ their 

 leisure time. One at least of the lost comets of short 

 period, is far more likely to be recovered in the southern 

 hemisphere, than in these latitudes. 



The Argentine Observatory.— Dr. Gould has just 

 circulated in two small pamphlets, in English, the annual 

 Report for 1874 of proceedings at the Observatory of 

 Cordoba, and at the Meteorological Office, which has 

 also been organised by this distinguished astronomer. 

 With regard to astronomical work, the observations 

 for the " Uranometry" are completed, as already men- 

 tioned in this column. The charts will be thirteen in 

 number, including the whole of the southern heavens as 

 well as the first ten degrees north of the equator, and 

 about 8,500 stars will be represented upon them, of which 

 about nine-tenths have southern declination. A catalogue 

 will accompany the Atlas, as with the works of Arge- 

 lander, Heis, and Behrmann. The zone-work was in a 

 very forward state, 82,537 stars having been observed, 

 and with the exception of an insignificant number of 

 zones for which it might be necessary to wait till a later 

 period of the year. Dr. Gould expected to complete this 

 laborious undertaking by the end of last month. The 

 third of the principal sub-divisions of work at Cordoba, 

 the formation of what is called " the smaller Catalogue " 

 is also well advanced : the catalogue is intended to con- 

 sist of nearly 5,000 of the brighter stars of the southern 

 heavens, each one observed not less than four times ; in 

 the year 1874, 12,500 observations of 3,600 different stars 

 were made, the greater number during Dr. Gould's visit 

 to his native city, a sufficient proof that he has been 



