424 



NA TURE 



[Sept. 14, 1876 



remain uncorrected. It will be seen in that figure that the eye, 

 and particularly the front convex surface of the crystalline lens, 

 makes the rays diverge, instead, of course, of making those that 

 catch the watery prism converge a little less. 



J. F, Blake 



Antedated Books 



I AM sorry to have to trouble you again under this heading, 

 but Mr. Sharpe's second letter necessitates a short reply. I did 

 not accuse Mr. Sharpe, in my original letter, of having wilfully 

 misdated his book, I never even mentioned his name. I merely 

 stated the facts and added a few comments to show that the date 

 was a matter of some importance. Mr. Sharpe is now angry 

 because I do not withdraw a charge which I never made. If he 

 had simply explained in his first letter that the misdate was an 

 error of his publisher and promised that it would not occur 

 again, the matter would have been ended. When he proceeded 

 to attack me for doing what I believed to be my duty, he naturally 

 provoked an unpleasant answer. F. Z. S. 



OUR ASTRONOMICAL COLUMN 



Variable Stars (i), Mira Ceti. — Herr Julius Schmidt, 

 Director of the Observatory at Athens, by a mean of 

 three sets of comparisons with S and y Ceti and a Piscium, 

 fixes the first maximum of 1876 to February 37, the date 

 inferred from Argelander's formula of sines being Janu- 

 ary 1 7'o. The minimum by the same formula occurred 

 on September i. 



(2) R HydrjE. Of this object, so difficult to observe 

 satisfactorily in these latitudes, Herr Schmidt observed a 

 maximum 1876, April I2'5. 



(3) The same observer refers to a secondary minimum 

 of the well-known variable star R Leonis, discovered by 

 Koch in 1782. For the present year his observations 

 have given the principal maximum May 77, the secon- 

 dary minimum May 217, a maximum June 17. 



(4) 16 Eridani. There appear to be grounds for add- 

 ing this star to the list of variables. It was considered 

 as high as 3-4 by Piazzi, 43 by Heis, 4 by Flamsteed, and 

 in the Washington general catalogue it is 4*4. Brisbane 

 calls it 6, Argelander, once 5, and once 6. Smyth says, 

 " it appeared more than once diminished to nearly a fifth 

 magnitude." — This star is also r* Eridani of B.A.C., but 

 as Bayer's map has no fewer than nine stars to which this 

 letter is applied, it appears preferable to adopt Flam- 

 steed's number. 



(5) We learn from Dr. Gould, that the variable star in 

 Musca, to which he has already directed attention, has 

 certainly a period shorter than that of any other known 

 variable star — or about thirty hours only. Its variation 

 is such that at minimum it is fairly beyond unassisted 

 vision in the sky of Cordoba, though distinctly seen at 

 maximum. 



(6) In a short list of variable stars stated by Dr. C. 

 H. F. Peters, of Hamilton College, Clinton, U.S., to have 

 been recently detected, which appears in Comptes Rendns, 

 1876, August 28, and in M. Leverrier's Bulletin Inter- 

 national, of Sept. 6, is ore in R.A. (i860), i5h. 13m. 21s., 

 N.P.D. 109° 53', said to vary between the sixth and 

 eleventh magnitudes. This star, however, is not new ; it 

 is No. '](i of' Schonfeld's last catalogue, and was dis- 

 covered by M. Borelley in 1872. Schonfeld's limits are 

 S'o and 12*5, the latter doubtful, and he assigns, as a 

 rough approximation to elements : 



Maximum 



1874, June 17+ 193** E. 



The first star on the same list is No. 6 of Schonfeld's list 

 in the introduction to his second catalogue (S. Libras). 



An Intra-Mercurial Planet (?). — The account of 

 the observation of a round spot on the sun's disc, re- 

 marked on April 4, but not seen either on the preceding 

 or following morning, which was quoted last week, from 



ninstitut of August 30, appears not to have been there 

 given accurately. By the Comptes Rendus of August 28, 

 we learn that M. Leverrier made the statement on the 

 authority of a letter from Prof. Rudolph Wolf, Director 

 of the Observatory at Zurich, dated August 26. Prof. 

 Wolf says : — " It will doubtless interest you to learn that 

 M. Weber, at Peckeloh, saw- on the 4th of April last, at 

 4h. 25m. M.T. at Berlin, a round spot upon the sun, which 

 was seen without spot on the same morning and on the 

 following one, not only by M. Weber, but also by me and 

 by M. Schmidt at Athens. (For the observation of M. 

 Weber, see No. 34 of the Wochenschrift fiir Astronoinie) 

 I remark that the date of M. Weber's observation follows 

 that of M. Lescarbault by 



6219 days = 148 X 42'i'02, 



which is curious enough on comparison with what I have 

 published on the subject at the time. See my * Hand- 

 buch der Mathematik und Astronomic,' vol. ii., p. 327." 



So that instead of the spot having been noticed in three 

 different and distant places, it was remarked at Peckeloh, 

 near Miinster only, though the observations by Prof. 

 Wolf, at Zurich, and Herr Julius Schmidt, at Athens, 

 establish the fact of the sun having been without the spot 

 in question shortly before and after its observation by Herr , 

 Weber, who is well known by his observations on the 

 zodiacal light and other phenomena. 



At present the particulars of the observation are not to 

 hand, but it is singular that Prof. Wolf's period of 42-02 

 days not only accords with the observation of M. Lescar- 

 bault, so far as regards an inferior conjunction of the 

 body with the sun on March 26, 1859, but it also agrees 

 with that of Mr. Lummis, March 20, 1862, and with the 

 one recorded by Decuppis at the CoUegio Romano, on 

 October 2, 1839, at the opposite node, at least within 

 probable transit-limits. Particulars of Mr. Lummis's 

 observation will be found in vol. xxii. of the Monthly 

 Notices of the Royal Astronomical Society ; that of 

 Decuppis was thus mentioned at the sitting of the Paris 

 Academy of Sciences, 1839, December 16 : — " M. De- 

 cuppis announces that on October 2, continuing the ob- i 

 servations which he had been making upon the spots 01 1 

 the sun, he saw a black spot, perfectly round, and with 

 border sharply defined, which advanced upon the disc, 

 with a rapid proper motion, such that it would have tra- 

 versed the diameter in about six hours. M. Decuppis 

 thinks that the appearances which he has observed can 

 only be explained by admitting the existence of a new 

 planet." 



If we were to accept the particulars of the various ob- 

 servations of a similar character as they are recorded, it 

 would be impossible to refer them to a single body, no 

 matter what the excentricity of the orbit might be 

 assumed to be, but most unfortunately these observations 

 have on no one occasion so far been taken by a practised 

 astronomer with proper micrometrical assistance. On 

 the contrary, they have mostly fallen to the lot of occa- 

 sional observers, who have contented themselves with 

 eye- estimations of position on the sun's disc, from which 

 little can be definitely ascertained. 



The Peckeloh observation of April 4 naturally suggests 

 frequent observation of the sun's disc from the middle of 

 the present month to the middle of October, particularly 

 about October 10. 



[Since the above was in type, we learn from a Paris 

 correspondent that M. Leverrier has made a further com- 

 munication to the Academy on the subject of an intra- 

 Mercurial planet or planets. Instead of a period of forty- 

 two days, as suggested by Prof. Wolf, he thinks one of 

 twenty-eight days more probable ; and this, it may be 

 observed, is an aliquot part of Prof. Wolf's period. But 

 notwithstanding a period of twenty-eight days accords 

 w^ith a number of the observations referring to round 

 black spots upon the solar disk, M. Leverrier is stated to 



