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have to await its next appearance in January 1866 for further information relative to its physical condition. This return will be looked forward to with much interest; as it will be important to know what changes may have occurred during the preceding 13 years, in the relative position of the two portions so strangely rent asunder, as already narrated-whether they still travel through space in company or not. That between 1846 and 1852 they had become, for all practical purposes, two complete comets, seems indisputable; and in the sweeping Ephemerides issued by the distinguished Superintendent of the Nautical Almanack, for facilitating their rediscovery in 1859, two perfectly independent sets of elements and positions were given. Henceforward, then, it will appear reasonable to speak, not of Biela's comet, but of Biela's comets.

(To be continued.)

ROYAL ASTRONOMICAL SOCIETY.

Second Meeting, December 8, 1865.

WARREN DE LA RUE, Esq., F.R.S., President, in the Chair. The minutes of the last meeting were read and confirmed. Twenty-one presents were announced, including the usual serials, and an interesting volume of observations at the Observatory of Joseph Gurney Barclay, Esq.

W. Jardine, Esq., B.A.,

H. S. Williams, Esq., M.A.,

O. H. Stokes, Capt. R.N.,

were balloted for and duly elected Fellows of the Society. The President stated that he was about to hold another soirée

at Willis's Rooms, on January 17, 1866.

The following papers were read :—

Three papers by Sir Thomas Maclear containing the R. A. and N.P.D. of Stars compared with the Comets of 1864-5.

Observations of the Lunar and Solar Eclipses of October 4 and 19, by Professor Chevallier, of Durham.

On Encke's Comet, by Mr. Smalley, of Sydney, N.S.W. Some places in June and July were given. The comet was very faint throughout its appearance, having no nucleus or tail, and being merely a patch of haze.

Note on Herculis, by Mr. Burr. Mr. Fletcher having remarked that this star, although now single in the largest telescopes was, a few years ago, measurable with 4 inches of aperture, Mr. Burr mentioned the 19th July, 1853, as a date when he saw it well separated with the smaller aperture of 3 inches. Paper on A Star Cluster in Perseus.

Observations of Comet III., 1860, by C. W. Moesta, of Santiago, Chili.

On the Telescopic Discs of Mars, by Mr. Stone. Attention having been directed to this subject it may be worth while to see what theory says on the question. This shows that the image of the star would be a small disc of light, surrounded by alternate intervals of darkness and rays of light, getting gradually fainter. The size would be independent of the focal length of the lens, and vary inversely as the radius of the aperture. A table of the theoretical intervals was given. It does not, however, follow that with all degrees of brightness the angular diameter varies inversely with the aperture; or small stars could be as large as bright ones. The theoretical result is for homogeneous light, and when the image is formed by a well-corrected objectglass the conditions of the theory are satisfied; but the subject becomes complicated by the different wave lengths of the colours. Still, it should follow that increase of aperture should diminish the image of a star. Haze passing over diminishes the light and decreases the disc. Mr. Stone quoted a paper by Mr. Dawes, in the Ast. Nach., and also Mr. Dawes' statement at the June meeting, that with a double image micrometer the discs were entirely dependent on the aperture, which was a confirmation of the undulatory theory; but Mr. Stone remarked that for this purpose it must be shown that the eye-piece of the micrometer and all other things remained the same.

The President enquired whether the size of the spurious disc did not depend in some measure upon the corrections of the object-glass?

Mr. Stone: Probably it would; but I have assumed the lens brings the rays to a correct focus.

Mr. Pritchard mentioned that in a conversation with Professor Miller, of Cambridge, he understood Mr. Miller to say that Steinheil stated that he made object-glasses so correct in form and perfect in material that the spurious discs were so large as to overlap and require the insertion of a glass of observation to see them double. This, said Mr. Pritchard, is an extraordinary statement, implying that he possesses glasses much more diaphanous than any of those of English or other German opticians. These large discs are not likely to be measurable; but the first ring, which everyone sees, is the second depending on aperture. Will Mr. Stone tell us if he has measured the first ring, and does its diameter vary inversely as the aperture? If not, the undulatory theory is at fault, and there is a residual phenomenon which may lead to the improvement of the theory of light. The transparency, and the qualities of the glass, and the state of the atmosphere, affect the size of the spurious disc, but not that of the first ring. I have ground more object-glasses than any man living-upon paper-and venture to say that any errors of aber

ration left in a good object-glass are out of the question as affecting the size of spurious discs of stars.

Mr. Stone: I have made no measures on the subject at all. At the last meeting allusion was made to the measures of discs, and I wrote this paper to point out the fallacy of this, and to show that the rings of light and darkness only are affected by the theory.

Continuation of Researches on the Physical Condition of the Sun, by M. Chacornac.

The President mentioned that he had referred to these observations in a paper which was printed for distribution after the meeting by Mr. Balfour Stewart, Mr. Loewy, and himself.

A Personal Equation in reading Microscopes, by Mr. Stone. This paper referred to Mr. Dunkin's on the difference of the determinations of the zenith point by different observers, and the explanation which Mr. Stone gave at the time, with some further details on the subject.

The President: How will it be with one observer?

Mr. Stone: If the same observer deduces the Nadir point and the G. Latitude there will be no error on this account; but at Greenwich the mean of all the observers is taken for the Nadir, and then the discrepancy appears. Long and short sight may make a slight difference. The extremes of the observations are half a second apart.

Mr. Dunkin mentioned an extraordinary confirmation of this equation in the case of a young person now training for an observer, who always said stars were bisected when they were not to Mr. Dunkin's eye, and when Mr. Dunkin bisected them it was denied by this young man.

Mr. Pritchard: I have seen a great philosopher not succeed in reading within 2". It is more difficult than you imagine; still, a careful man will do well without practice. The late Andrew Ross, using my circle, after two trials, made 10 bisections running, not differing the 10th of a second. Will Mr. Dunkin say what difference the same observer makes?

Mr. Dunkin: A practical observer will hardly differ fivethousandths of a second.

ence.

Professor Challis: The difference does not depend on inexperiI had a good observer at Cambridge who always differed in his readings from mine, though they were quite consistent among themselves.

Mr. Stone: There must be something abnormal about the eye of the young man at Greenwich; his intervals differ from

+03. I don't know what we shall do with him.

-0°4 to

Mr. Dunkin: You are not referring to the same person that I am.

Mr. Stone: Then I am sorry to find there are two of them. On the Physical Constitution of the Sun, by Capt. Ashe, Director of the Quebec Observatory. The author observes with a telescope of 8 inches aperture, by Alvan Clarke, and remarked that if the sun be an incandescent body, throwing off heat, that heat must be restored in some way, and a theory that explained this must be better than others. Until he used a large objectglass he thought the spots were cavities, but now he could see they were masses floating on the surface. In the case of spots without penumbra, the cavernous theory required a long tunnel through the photosphere, and the inclination of its sides must alter as the sun rotated. He quoted Mr. Carrington and Mr. Birt to show that difficulties existed on the usual theory, especially as to the floating away of the penumbra sometimes, and then stated his conviction that the sun is a nebulous star, having an equally bright photosphere; that the spots are some of the meteors which revolve in a zone round the sun falling on to it and melting, the penumbra being the dross or filmy portion of the attenuated surface, and the faculæ the breaking-up of the scum. Among the facts and arguments supporting this theory Captain Ashe claimed that it accounted for the periodicity of the spots, and for their connection with the position of Venus. He thought the zodiacal light constituted the nebula of the sun, and was composed of atoms smaller than the meteors which fall to the earth. These bodies falling on the sun form small spots at first, which melt and enlarge, the dross forming the penumbra-this sometimes breaks and shows bright bridges. The rose-coloured prominences of eclipses, he thought corroborated his view, and he quoted, in conclusion, Dr. Wollaston's account of a spot shivering to pieces, like a block of ice, as a further argument in his favour. The President observed that, as he had often said, we want observations, and while there is no harm in theorizing it is clear that at present no theory embraces all the facts. The falling in of meteors to restore the heat was Thomson's theory, but he thought it was rather given up at present. Unfortunately for Captain Ashe's theory Mr. De la Rue's measures of the foreshortening of spots as they altered from the sun's rotation, were adverse to it, as, out of 530 spots 86 per cent. showed that the nucleus was lower than the sun's surface, and only 14 per cent. against it.

Mr. Glaisher gave an oral account of the Luminous Meteors seen at Greenwich on the 13th November last. Notice of the expected shower having been given, 6 observers were appointed to watch on the night of November 12. All the usual days for meteors appearing are watched; but never before has the November period been found to give a fine display. From 6 to 8 o'clock, p.m., only 2 meteors were seen; from 8 to 12 was cloudy; from

12 to half-past only 1 appeared, but by 1 a.m. 29 had been recorded; from 1 to 2, 90 were observed; in the next hour, 66; and by 5 o'clock 280 had been carefully observed as to size, colour, path, &c., while so many more had been seen that they must have been passing at the rate of 250 an hour. For each one seen it may be assumed 2 were lost; so that at least 1,000 must have appeared. Mr. Glaisher exhibited a diagram of their paths, and compared it with a chart of Mr. A. Herschel's observations at Hawkhurst, where a smaller number showed one radiant point, and that one of the 57 well-determined ones. At Greenwich the results had the same tendency, but were not quite so abundant. The connection of this subject with astronomy is, that the radiant point of these meteors is in Leo, and it is to this direction that the earth is travelling. This is the first time for 20 years that the November meteors have been well seen at Greenwich. Observations have been made many times a-year, and the records of isolated meteors made, when compared with others, have been of use in determining the radiant points. On this occasion the radiant point was about 165° R.A., and 60° N.P.D. More than half of the meteors were blue, the majority of the remainder being white. Nearly all were equal to first magnitude stars, and some as fine as Jupiter and Sirius, and nearly two-thirds had tails or trains of sparks.

At Cambridge Mr. Adams had observed some of the meteors, and good results had been obtained at Manchester and other places. Out of 15 of Mr. Adams's list, which were found to be the same with Mr. A. Herschel's, 7 gave the distances of the meteors as ranging between 79 and 114 miles from the earth. Further information would be gained when the observations had been reduced.

The President remarked that the number of meteors seen would depend upon the radiant point being above the horizon, and the number being great proved how accurately the point had

been determined.

Mr. Glaisher said the time had been foretold within an hour or so, and that it was likely a finer sight would be seen on November 14 next year.

Mr. Pritchard: Did you see the maximum number of meteors when the point towards which the earth was moving came above the horizon?

Mr. Glaisher: Our observations were the reverse of this. From the numbers and paths we deduce the radiant point; but it comes to the same thing.

The President: When did Leo rise?

Mr. Glaisher: About 12. The maximum was taken; but in the preceding 6 hours we saw only 2, proving the accuracy of the predicted time.

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