moderate powers it requires good air to show nicely the companions of 72 P Cassiopea and Orionis: these stars are more difficult with the reflector than many much closer. On this kind of stars I find a full aperture and high power answer better than a lower power and contracted aperture. When I first got my telescope, I was much annoyed by observing, when looking at bright objects,--large stars, for instance,―a very conspicuous vertical ray and a fainter horizontal ray proceeding from the image. I thought at first that this must be caused by bad figuring of the specula. After trying experiments, however, I have found out that these rays proceed from no such cause, but from interruption of the incident light. The more conspicuous vertical ray is caused by the horizontal arm carrying the flat mirror. The less objectionable horizontal ray proceeds from the shape of the flat mirror, which is rectangular, and not oval. I have no doubt that also a slight vertical ray is caused by the rectangular flat; but this will be swallowed up in the stronger ray caused by the arm. It is easy to see that the arm of the Newtonian must cause a ray; for if a thin piece of stick, or even a thread, be placed before the mouth of the reflector, and slowly moved while the telescope is pointed to a bright star, a movable ray is at once visible. To make sure that the arm was the cause of the stronger vertical ray, I took away the horizontal arm and fastened the flat on a vertical arm: when this was done, the strong ray took up a horizontal position. This must be well known by most passessors of Newtonians; but still I think that by many the surface of the flat mirror is blamed, and the true cause--the interception of the incident light by the small mirror, and especially by the arm-is overlooked. July 18th. I am, Sir, yours very truly, W. MATTHEWS. P.S.—Mr. Freeman, in the last number of the Register, mentions some interesting double stars, and some tolerably difficult. As Mr. Freeman's telescope, although not a large one, seems a good one, I will name a few stars some of which, I think, will be found about equally difficult, and some a little more difficult, than those named: Ophiuchi, 12 Lyncis, 72 P Cassiopeæ, 36 Andromedæ, e Arietis, n Orionis, Bootis, e Equulei. The three last-named stars are perhaps rather difficult for a 4 aperture, and do not exceed 1" in distance, I think. 32 Orionis is far too close for a 4-inch. I should have thought that Mr. Freeman might possibly have seen & Cygni. I have never yet seen the companion to this star in a perfectly satisfactory manner with my 8-inch reflector; but, at the same time, I feel sure that I have sometimes detected the small star. A PLANETARY REMONSTRANCE. TO THE EDITOR OF THE ASTRONOMICAL REGISTER. Mr. Editor,-Any person with proper feelings of self-respect, after the toil and labour of 84 years, would feel somewhat hurt and offended I am at being neglected or overlooked. I have now been toiling for that period with slow steps on my weary way before your eyes, and have completed one entire circuit the grand tour in the far-off heavens-yet none of you astronomers have offered me your congratulations. The R.A.S. should be ashamed of themselves. They continued their meetings up to June, yet no "notice" of me. Allow me to mention one incident which, I think, will stamp your conduct with ingratitude. In this journey I have been, as usual, very much attracted by a distant relative, unknown to you for a long time. When, however, through me (and altogether through me), you became acquainted with him, you were all filled with joy, and gave to Neptune such a reception as I never received. Since all this rejoicing and increase of happiness to you was owing to me (and not either to M. Leverrier or to Mr. Adams), I do think you might have taken the opportunity of the completion of my 84th year to pay me some special attentions. I am truly amazed: not even one stanza of poetry have I heard or seen. sure I deserve something of this kind as well as that moon of yours. But, not to dwell longer on this painful subject, I wish to say to you that I will pardon the past, provided you will at once make some reparation to my eclipsed brilliancy, my wounded feelings. My four satellites (there now you are told the great secret-I have only four) are most indignant; they flare up and say that we should pass you by in silent contempt, as unworthy our notice. I do not wish to act thus proudly or unkindly, especially towards you; as, although you inhabit such a little bit of a planet, I do think there is some excellence in you. You cannot see as far as your own eagle, nor run with the speed of your reindeer; yet you far, far exceed the one in seeing, and the other in swiftness. All of us, too, think highly of your intelligence and address (my indignation made me indisposed to acknowledge this above) in making the acquaintance of my distant relative to whom I alluded. For these reasons I do not wish to be found in opposition when you may expect me to be in harmony and conjunction. Consider, then, what I have achieved, notwithstanding all my perturbations, long retrogressions, and many occultations, since 1781. I arrived in 1865, the moment I was due, according to my very worthy son's (J. R. Hind's) time-tables, at my appointed place, near those youths, whom I found as young and beautiful as ever, and who are still as like as two twins, in whose neighbourhood I mean to stay, though moving about as usual, for about seven years. At any time you wish to see me during these years, I will be found at the sign of the Crab. Consider all this, and make reasonable acknowledgments of my glorious career since the day you first knew me (notwithstanding some injust insinuations of unsteadiness), and thus restore good feeling between us. Since I have given up the aliases I once had, I sign my name at all times, and in all places, as I do now, and am, Yours as you may deserve, URANUS. P.S.-I trust you will not put off paying me the expected attentions until I come round again. Pray, where shall I find you all then!! Who will be the Astronomer-Royal? Who will be the Editor of the Astronomical Register? Alas, alas! Truditur dies die, novæque pergunt interire luna. Yours, U. THE LIBRARY OF THE ROYAL ASTRONOMICAL SOCIETY. TO THE EDITOR OF THE ASTRONOMICAL REGISTER. Sir, I wonder whether the Council have ever had their attention directed to the flagrant violations of their rules regarding the Library now and for a long time past perpetrated. The number of books borrowed from the library and returned, I won't say at, but within a few weeks of, the proper time laid down by the regulations, is not I per cent. of those that go out. The result of this is that a great amount of inconvenience is caused to country members (like myself), many of whom are only in London at distant intervals; and I doubt not that many of your readers will confirm me in this expression of opinion. If the present regulations are bad, alter them or abolish them; but it is a hollow mockery to lay down laws that books are to be returned within two months (or whatever the time may be), and then to allow members, with impunity, to keep them two years. I have no wish to advocate unfair or inconvenient restriction; but I do say that members ought to be summarily prevented from filling up empty shelves in their bookcases with the Society's books, never looking into them themselves for months at a stretch. This is not use, but abuse, to which members themselves ought to be ashamed to be parties. I am, Sir, your obedient servant, May 10, 1865. A PRACTICAL MAN. JUPITER'S SATELLITES. TO THE EDITOR OF THE ASTRONOMICAL REGISTER. In answer to an enquiry by Mr. C. Grover, in the last number of the Register, page 212, as to whether an appearance of penumbra has ever been observed in connection with the shadows of Jupiter's satellites, the Editor begs to give a copy of the entries in his note-book respecting such an appearance observed by himself. 1861. Feb. 28.-12h. While trying the 6-foot telescope upon Jupiter, I observed a dark spot on the planet, and knowing that the 3rd satellite would cross the disc some time during the evening, I concluded it to be the shadow of the satellite. I was therefore surprised when, looking again about 14h., to observe the shadow just then well on to the following limb of the planet, the spot I had taken for the shadow being really the satellite. The shadow was nearly twice as large and much darker than the satellite, and had a shade or appearance round it like the penumbra of a solar spot, which it somewhat resembled. 1861. Mar. 3. (The 4th satellite).—9h. 29m. Shadow just within Jupiter's limb.-9h. 32m. Satellite just clear of Jupiter. As the satellite left Jupiter's limb, it appeared like a small projection of the dark equatorial belt, to which it was precisely similar in colour. The shadow was much darker than the satellite had been, but the air was not steady enough to enable me to observe if there were any penumbra. 1861. Mar 29.—7h. 20m. The colour of the shadow of the 1st satellite is grey; that of the 3rd, intense black. Although there is much smoke in the air, the definition on Jupiter is superb. -7h. 35m. The white breaks in the belts of the planet are now coming on at the following limb. I again observed the shading off of the shadow of the 3rd satellite, giving the appearance of a penumbra. These observations were generally made with a telescope of 39 in. aperture and a power of 100. A note on the subject was sent to the Royal Astronomical Society, which is alluded to in the Monthly Notices for March 1861, vol. xxi. p. 169. Downs Road, Clapton: August 14, 1865. NOTES AND GLEANINGS. RELATIVE BRIGHTNESS OF VENUS AND THE MOON.-At 3 a.m. on the morning of June 20, M. Chacornac conducted some observations near Lyons, with the view of comparing the relative luminosity of the above-named objects. The apparatus used is not described, further than that it was a species of polariscope. A brilliant portion of the moon between the craters Rocca and Erchstadt, SE. of Grimaldi, was isolated from the rest of the disc, and the final result arrived at was that the luminosity of the most luminous part of the moon's surface was only one-tenth that of the surface of Venus. M. Chacornac could not detect any trace of polarised light in Venus, though it was very noticeable in the moon; and he considers that the light which we receive from Venus is reflected from a continuous surface of clouds, and that the spots seen on its disc are not, as De Vico supposed, permanent ones. THE VARIABLE STAR T. PEGASI. M. Argelander finds that the changes in the light of this star may be fairly reconciled to the assumption that its period is 374 days. NEW VARIABLE STAR.-Dr. C. H. F. Peters, of Clinton, Ohio, has communicated to the Astronomische Nachrichten an account of two stars which he has ascertained are variable. Their positions for 1865 are Decl. II 31 31 + 4 7'1 ... The usual magnitude of No. 1 is 10, and the period seems to be some multiple of 4 years. The second star appears to vary between the 10th magnitude as a maximum, and below the 14th as a minimum. THE TEMPORARY STAR OF 1604 has recently occupied the attention of M. Schönfeld, of Mannheim. He considers that its position for the epoch of 1855 is represented by the following coordinates: R. A. Decl. 17 21 57... -21 212 the annual variation in R.A. being + 3586", and in declination -0055'. We gave Winnecke's results in a former number of the Register. Winnecke's figures are greater by 4m. 108. in R.A., and 5°9′ in Decl.; a discordance not large when we consider the fact that 261 years have elapsed since the star was observed, and the looseness with which astronomical records were kept two and a half centuries ago. Observers with large telescopes would do good service by constantly scrutinising the heavens in the above neighbourhood, to see whether there are any traces of a variable to be found. THE MINOR PLANET JUNO is favourably situated for observation this month, and has an apparent magnitude of 7.6. This is one of the first discovered of these interesting bodies, of which upwards of eighty have now been detected between the orbits of Mars and Jupiter. The following positions will be useful to those who have access to an equatoreal. The planet passes the meridian about 12 o'clock at the beginning and about half-past 10 at the end of the month. COMETS.-In answer to "B. A." (Register for June), the computation of a comet's elements from three observations is given in the Mécanique Céleste.-G. L. T. BINARY STARS.-May I suggest the desirability of a periodical, say annual, statement of the distances and positions from time to time of the most prominently interesting binary star systems? If some one, thoroughly competent and willing, were to furnish such measures of a reliable character, they could not fail to be an acceptable addition to the information given to the readers of the Register. T. W. SCHRÖN'S LOGARITHMS, to seven figures, 5th Edition, stereotyped. Williams and Norgate.-Professor De Morgan, who has prefixed a description, thinks this the best 7-figure table he has seen, and extremely correct. Copies are to be had on paper of a light green tint. |