INSTRUMENTS, &c., FOR SALE.

These Notices, which are restricted to two lines each, are inserted free of charge to subscribers: applications respecting them to be made to the Editor, with a stamped envelope for reply, without which no answer can be sent.-For Advertisements with more complete details a small charge will be made.-N. B.-It is particularly requested that we may be informed when instruments are disposed of, in order that the notice may be withdrawn, and fruitless applications prevented.

Achromatic Refractor, 7in. ap., 9ft. focus, by Troughton &Simms; 6 eye-pieces; on garden Equatorial, steadying rods, &c. [54] Achromatic Refractor, 6 4/10 in. ap., 8 ft. focal length, by Merz, Equatorial and clockwork, by Troughton & Simms. [73] Achromatic Refractor, 5 ft. 3 in. focus, 4 in. ap., by Cooke & Sons; finder, 2 in., 3 eye-pieces, illuminating apparatus, no stand. [68] Achromatic Refractor, 3 in. aperture, 42. in. focus, 4 eye-pieces, finder, &c. Equatorially mounted. [67] Achromatic Refractor, 4ft. focus, 23in. ap., 3 pancratic eye-pieces, powers 60 to 200, pillar and claw, and garden tripod stand. [61] Achromatic Refractor, 2 in. ap., 42 in. focus, on tall tripod, finder, 6 eye-pieces, sun shades, illuminating mirror, &c., in case, [62] Achromatic Refractor, 2§ in. ap., 42 in. focus, one day and one night eye-pieces, on tall tripod stand.

[72]

[63]

Gregorian Reflector, 4in. ap., 2ft. focal length, by Dollond, 4 powers, 50 to 200, finder, &c., on brass table stand. Newtonian Metal Speculum, 8 in. diameter; first-class quality.

[77]

Transit Instrument, 5 ft. focus, 3 in. aperture, Ys fitted with agates, for mounting on stone piers. [29] Equatorial Stand, for a 5 or 6ft. telescope: 13in. circles, divided on silver, to 10"of space and 4s. of time,-Has never been used, [55] Improved Varley Stand, rackwork movements, for a telescope of 5 or 6 ft. focus: on circular turn-table, to point in any direction. [16] Polar Axis of mahogany, 7ft. long, adapted for a 4ft. telescope, with 12in. circles, reading to minutes.

[56] Speculum Grinding Apparatus, capable of working a 7ft. speculum with tube and fittings for a 9in, Newtonian. Recreative Science: complete in numbers, half-price.

[57] [30]

QUATORIAL TELESCOPE and STAND, by T. SLATER,

Telescope has been used in a private observatory three years, and its performance on of its late owner

close double stars guaranteed: it has been removed in consequencer.

having purchased of the same maker an object glass of 16 in.

[80]

CHROMATIC REFRACTOR, 3 in. aperture, 42 in. focus, four

with circles reading by microscopes to 2 seconds of time and 10 seconds of arc; level, rack, and clamps in R. A. and Dec., &c. Price £34. 0[67]

a

TO BE SOLD, 3 12 in. SILVERED GLASS SPECULUM,

greatest ease.

FOR

[78]

NOR SALE-an EQUATORIAL LADDER STAND. Price £3. -Price £15. Both in good condition. Apply to F.R.A.S., Ockbrook, Derby. [74]

INSTRUMENTS, &c., WANTED,

Wanted, a Transit Instrument, 18 or 24 in. focus, 2 in. aperture. Apply to John Stead, Stanwix, near Carlisle. Equatorial Stand, Wanted-adapted for a 5 ft. Refractor, with graduated circles; second hand, at a moderate price.

[71]

[35]

Monthly Notices of the Royal Astronomical Society.-The third Volume wanted: a good price will be given.

Celestial Globe wanted, not less than 18 in. in diameter, with the necessary circles.

[26]

[70]

Astronomical Clock, wanted immediately; not necessary to be a very first class one, therefore the price must be low.

[65]

Map of the Moon-a copy of the German edition of Beer and Madler's large map wanted.

[69]

The Bedford Catalogue.-Wanted, a copy, complete and in good condition, of Smyth's Cycle of Celestial Objects. Astronomical Register, No. 5.-Three Shillings will be given for a clean copy of this number.

[75]

[79]

ANTED TO PURCHASE, A GREGORIAN REFLECTOR,

[76]

stand.

TWO FULL MOONS IN THE SAME MONTH.

TO THE EDITOR OF THE ASTRONOMICAL REGISTER. Sir,-Pray do not be alarmed when I propose to write a few lines on the Moon and her movements. I do not mean to discuss whether she revolves or rotates. That question may rest in peace, covered thickly over with the dust which was raised about it. That long controversy may well be called "much ado about nothing," as there was no difference of opinion whatever regarding any motion of the moon, or any phenomenon connected with her motions.

But now for my small talk about the said moon. The opening of the present year reminds me of a terrible commotion which arose in a village on the east coast of Kent, when they discovered that there were to be two full moons in the same month (July 1852). I recollect that a deputation waited on me to know my opinion concerning it. They all calculated on Plague, Pestilence, and Famine." I endeavoured to quiet their minds and to show them that if there were not two full moons in that month, there would be real cause for alarm-the heavenly bodies were going astray, and all nature might break up. I thought of these simple people this January 1866, when true to the theory of the Metonic Cycle we have our two moons, followed by a blank in February, and of course, two more full moons in March. What would our eastern villagers think of this year! They must add to plague, pestilence, and famine, the other three sore scourges, battle, murder, and sudden death, unless indeed, as we should hope, that the light of science in its onward march, may have reached them, and dissipated the dense cloud which enveloped them. Together with alarm at two full moons in the same month, they all held that there are 13 moons every year. If this were the case, I endeavoured to show them we should have two full moons in some one month every year, but that this event happened only every 3 years less 3 or 4 months, as there were only 12 moons and about one-third of the next moon in each year.

Strange to say that two of our most popular almanacs, Dietrichsen's and the Illustrated, (which are excellent in general on Astronomical subjects), are this year very much at fault in the full moons of January and March. The former omits altogether that of January 1, and places that of March I in February. The latter (the Illustrated London) omits the full moon of January 1, and gives doubtful notice of that of the 30th, as it marks new moon on that day (see page 2). The March full moons however are correctly given

in the Illustrated at page Io. As Almanac makers are the wisest and most accurate in such details, the above inaccuracies surprise us.

The last year in which we had two months with two full moons in each, was of course nineteen years ago, in 1847. The intermediate years between 1847 and 1866 which gave us two full moons in one of their months, were 1849, 52, 55, 57, 60 and 63. Having these numbers, we can go forwards or backwards, using the metonic cycle, we may then learn how beautifully regular our satellite is in all her movements, and that the expressions" errantem lunam" of the ancients, and our "tickle," "uncertain,' ," "straying" moon, are proofs of our readiness to bear false witness against our neighbour rather than acknowledge our own dulness and want of accurate knowledge. I intended saying something on the influence of the moon on the tides in our atmosphere, and on the flowings of thoughts in the minds of men, as well as her acknowledged power over the flowings in our waters and tides in our oceans, but I forbear, lest I might, by my wandering, shut out all chance of your receiving favourably my communication, already much too long for the stinted pages of your Register. It will account for, if not excuse, my loquacity, when I tell that this year is the fourth year having two full moons in January and March which I have witnessed since I began to look up at the starry heavens, viz. 1809, 1828, 1847 and 1866. I remember the comet of 1811 as well, if not better than that of 1861, notwithstanding the fifty years interval. I am, therefore, entitled to claim the privilege of an old man, and sign myself, yours obliged, Edwards Terrace; January, 20, 1866.

you

SENEX.

RETURNS OF PRIVATE OBSERVATORIES.

Of Forty eight Observatories, particulars of which have been received by the Editor of the Astronomical Register, thirty two are provided with Equatorial Refractors; eight, with Horizontal and Vertical Refractors; seven, with Reflecting Telescopes; while one has no extra-meridianal instrument.

Of these forty seven telescopes, fourteen are driven by clockwork. Fourteen of the observatories are provided with Transit Instruments, and nineteen with Clocks.

The following are some particulars relating to the instruments :—
Apertures of the Telescopes, in inches.

The returns, from which these particulars have been taken, are now in Mr De La Rue's hands, who has also received a considerable number independent of the above.

ELEMENTS OF QUATERNIONS, by the late Sir W. R. HAMILTON.This work occupied a very large share of the life and attention of the late Royal Astronomer of Ireland, who did not live however to see it published. That task has therefore been undertaken by his son, and the work has just been issued by Messrs Longman. The author published some lectures on the same subject several years ago, and although the present work is in plan entirely

new, it is founded upon principles contained in those lectures. The work is divided into three books; the first treating of the Vector; the second, of the Quaternion; the third, of the products and powers of the former, regarded as constituting a second principal form of the latter. In our next number we hope to present our readers with Mr Pritchard's able memoir of the author, in which the work before us is specially referred to. The subject is a very deep one, and only to be understood by geometers and mathematicians of the most advanced character.

A TOTAL ECLIPSE OF THE MOON, partly visible at Greenwich, will take place on Saturnay morning, March 31, about half past I o'clock.

19 39

The first contact takes place 98° from the north point of the moon's limb towards the east, and the last contact 63° from the same point towards the west, for direct image.-Magnitude of the Eclipse (moon's diameter=1) 1*520. The Moon sets at 17h. 43m.

Now ready, in 8vo. pp. 812, price 25s. cloth,

LEMENTS of QUATERNIONS.

By Sir WILLIAM ROWAN

land. Edited by his SON, W. E. HAMILTON, B.A., C.E.

LONDON: LONGMANS, GREEN, and CO, Paternoster Row.

LIST OF SUBSCRIBERS-Names received since our last number.

Boys, H. Esq., Jesus College, Cambridge.

Cross, Rev. J.E., M. A., F.Ř.A.S., Appleby Vicarage, near Brigg, Lincolnshire Drage, C.P. Esq., Rose Cottage, Chesterton Lane, Cambridge.

Lawrence, E. Esq., B.A., 94, Westbourne Terrace, Hyde Park.

Rossendale, A. Esq., Walden House, near Oswestry.

Terry, J. Esq. 109, Borough Road, S. E.

TO

CORRESPONDENTS.

Several Communications, most of which are in type, are deferred for want of space. The letter of our correspondent who charges us with 'partiality' and 'want of courage' is marked private, otherwise we would have printed it in our own justification: we must ask his permission to let us do so in our next number.

ERRATA.-No. 38, p. 39, In list of Fellows elected-for Frederick Thomas Hughes read Frederick Robert Hughes, and for Capt. Charles Thomas Kerr read Capt. Charles Thomas Curme.

The Astronomical Register is intended to appear at the commencement of each month: the Subscription, (including Postage) is fixed at Three Shillings per Quarter, payable in advance, by postage stamps or otherwise.

The pages of the Astronomical Register are open to all suitable communications: Letters, Articles for insertion, &c., must be sent to the Editor, MRS.GORTON, Stamford Villa, Downs Road, Clapton, N.E., not later than the 15th of the month.

The Rev. C. PRITCHARD, F.R.S., President, in the Chair. The President, on taking the chair, said: I cannot assume the position in which you have placed me without saying that, as I now find the Society in a prosperous condition, and the meetings cheerful and harmonious, I sincerely hope, at the end of my term of office, to leave the Society even more prosperous and the meetings equally agreeable.. I must also say one passing word on the absence this evening of one venerable face-a face which was never absent from our meetings when it could possibly be present, and who, so far as material assistance is concerned, was the best friend the Society ever had. (Applause.) I am gratified to find by your reception of these remarks that I have your sympathy in what I have said, and that I should not properly have represented you had I passed over the loss we have sustained in silence.

Mr. Mummery inquired whether it was usual in the Society to pass a vote of condolence on such occasions; and if so, he should be glad to propose it.

The President replied that it was not usual to do so, and, looking to the time the Society had existed, he feared such events must be expected to become more frequent, and it was, therefore, not desirable to make a precedent. The Council, however, in anticipation of the feelings of the members, had commissioned him to write to Mrs. Lee expressing their regret at such a melancholy event, as well as their appreciation of the value of their late colleague, and their own loss by his removal. Another sad deprivation had to be referred to―viz., the death of Dr. Whewell, one of the oldest members of the Society, whose funeral would prevent the Astronomer Royal's presence this evening to explain the interesting paper of M. Delaunay-Mr. Airy having left for