Astronomical Register: A Medium of Communication for Amateur Observers and ...

SATURN.

TO THE EDITOR OF THE ASTRONOMICAL REGISTER. Sir,-During a series of careful observations of Saturn, I have noticed a peculiarity in that system which, not having seen it referred to elsewhere, I am induced to record for the future notice of students of this wonderful planet. I have on many occasions carefully studied the shadow of the planet on the ring, and although its boundary line is well defined, sharply cutting off one arm of the ansæ from apparent contact with the ball, yet I always notice that those parts of the ring immediately adjacent to the boundary of the shadow are of inferior brightness to the other parts of the ring, and that the obscuration is greatest close to the boundary line of shadow, the rings recovering their full brightness gradually from this line; thus it appears, that although the bounding line of real shadow is plainly apparent, it is fringed by a penumbra, or partial shadow, apparently caused by the sun's disc being partially eclipsed to these portions of the rings; the appearance would seem exactly the same as the penumbra seen on the moon during a lunar eclipse, or the penumbral shadow of the earth during a solar eclipse.

The appearance is peculiar and well worthy the attention of observers of this peculiar planetary system, and it would be interesting to know if any observer of the transits of Jupiter's moons has detected any appearance of a penumbra (similar to what occurs on the earth surrounding the shadow of our moon) surrounding the shadows of the Jovian satellites.

I am, Sir, yours very truly,
CHARLES GROVER.

Red Lion Street, Chatham, Bucks:
July 19, 1865.

PHOTOGRAPHY AT GREENWICH OBSERVATORY.-Under this title Mr. Burr has contributed to the Intellectual Observer for August an interesting account of the apparatus and processes used at our National Observatory for the continuous self-registration of magnetic and meteorological phenomena, prefaced by a brief though valuable sketch of the leading objects of the Science of Terrestrial Magnetism. Besides other illustrations, the article contains a fac-simile of one of the photographic sheets, engraved by the permission of the Astronomer Royal.

LITERARY NOTICES.

OLBERS'S TREATISE ON COMETS.-A new edition of this able work, edited by J. P. Galle, has just been issued at Leipzig. The former edition was published in 1847; the present one contains an epitome of all the comets discovered since then, with a full statement of their elements.

THE PLANET SATURN.-Will some one give us a short account of Mr. Proctor's recent work on Saturn? G.J.W. [The following is extracted from Messrs. Longman's List.-ED.] "The object of this volume is to present a fuller account of Saturn and its system than can be given in astronomical works having a wider range. The work treats of-The motions (real and apparent) and telescopic appearance of Saturn, its satellites and rings; the great inequality' of Saturn and Jupiter; the nature of the rings-showing that they are not continuous bodies, solid or fluid; and the habitability of Saturn— proving, inter alia, that the eclipses caused by the rings continue (in places) for many years, and extend (at times) over vast regions of Saturn's surface. Three Notes are appended in which the author has endeavoured to show :-That Chaldean astronomy formed a more complete system than is commonly supposed; that LAPLACE'S Nebular Theory is not opposed to modern scientific discoveries, to just views of the wisdom and power of God, or to the Scripture account of creation; and that the arguments for and against the existence of a lunar atmosphere may be reconciled by a theory founded on the moon's colour. Among the tables (which, with explanatory notes and explanations of astronomical terms, form APPENDIX II.) will be found :— Elements for determining the appearance and illumination of the rings, to the year 1900; the dates of the passages of the rings' plane through the sun between the years 1600 and 2000; and the climatic relations, appearance of the rings, and duration of eclipses caused by the rings, for different latitudes on Saturn's globe. The author has endeavoured to make the engravings represent as exactly as possible what they are intended to illustrate.'

STAR-MAPS.-Messrs. Longman & Co. are preparing for publication in royal 4to. (engraved partly on steel and partly on wood), a series of STAR-MAPS, by RICHARD A. PROCTOR, B.A., author of 'Saturn and its System.' The stars on a 6-inch globe will be projected from the centre upon the circumscribing dodecahedron, forming Twelve MAPS much less distorted than the Useful Knowledge Society's Six Maps, which are projected on the circumscribing cube; and by presenting the Twelve Maps on two plates, each consisting of Five Maps surrounding a polar pentagonal map, the relative positions of the stars of each hemisphere will be seen at a glance. Duplicate Maps on wood will exhibit the stars on a black ground.

"ASTRONOMICAL INVESTIGATIONS.-The Cosmical Relations of the Revolution of the Lunar Apsides and Oceanic Tides," is the title of a book by Dr. H. F. A. PRATT, recently published by Churchill and Co.

RÜMKER'S VARIABLE STAR.

M. Goldschmidt has communicated to the Bulletin Météorologique some remarks on the star mentioned by Rümker, in Vol. VIII. of the Monthly Notices of the Royal Astronomical Society, as probably variable. He thinks its variability to be quite certain, and that the period may be 44 years or thereabouts. In his telescope (one of about 4 inches, we believe) it disappears entirely.

OBSERVATION OF A SUPPOSED NEW INFERIOR

PLANET.

FROM Le Bulletin International.

The following letter, dated Constantinople, May 10, 1865, has been addressed to M. Le Verrier, by M. Aristide Coumbary::

"I take advantage of an opportunity of communicating with you which has unexpectedly occurred, to make you acquainted with an observation made by me on May 8.

"It is my custom to direct my telescope from time to time on the sun for the purpose of observing the solar spots; and during the month of May, in particular, my scrutiny is very constant, for, to tell you the truth, the temperature at that period of the year indisposes me to active exertion. On May 8, I was observing the sun according to my custom, and about 9h. 28m. I fancied I saw a little black point detach itself from a certain spot. I did not feel quite confident that that was the case, and thinking my eye might be at fault, I rested awhile; again examining the disc, a further proof awaited me that I had not been deceived, for I found that the black point had departed from the spot to the extent of twice its former distance. This time I discovered that the black point had a circular outline, and moved minute by minute. The power I was using was 140, but I changed this for a higher one, to wit, 280. This enabled me to distinguish very plainly the movement of the black body, but the loss of light rendered the outline less clear. From the time I first saw the object till its final disappearance off the sun's limb, a period of about 48m. elapsed. Just before the disappearance the outline became oval, and seemed to show a central separation as if there were two bodies in close contiguity, but of this I am not certain, for perhaps my eye, being fatigued, was at fault, or the eye-piece had something to do with it.

"I deem it my duty to lay this observation before you, as it may serve as a basis for further observation."

whether 280 as

[It is not quite clear what the second power was, I have given it, or 250; the original, being in manuscript lithographed, is indistinct. The oval outline mentioned would seem analogous to the "pear-shaped outline" spoken of by various astronomers who have observed transits of Venus. From the diagram sent by M. Coumbary, it may be inferred that if the portion of the transit seen by him occupied 48m., the whole duration would probably have amounted to one hour or a little more. The least that can be said is that this communication is a very interesting one.-G. F. C.]

THE ACADEMY OF SCIENCES.-M. O. Struve has just been elected a corresponding member of this academy. The other candidates were Professor Challis, Dr. Robinson, and MM. Galle, De Gasparis, Graham, Hencke, Lamont, Lassell, Littrow, and Plantamour.

THE NEW PLANET BEATRICE.

The following elements of this planet have been calculated by M. Becker :

Epoch. 1865. May. 4'5 B.M.T.