ROYAL ASTRONOMICAL SOCIETY.

Third Meeting, January 12, 1866.

WARREN DE LA RUE, Esq., F.R.S., President, in the Chair. Secretaries-Rev. C. PRITCHARD and E. J. STONE, Esq. (pro tem.) The minutes of the last meeting were read and confirmed. Twenty-five presents were announced, including two works by Professor Hansen and M. Delaunay to which the President drew especial attention, remarking that, although of very different bulk, they were, perhaps, of equal importance. One was the 2nd volume of Hansen's Lunar Theory, which would afford an opportunity of comparing observations with his formulæ, particularly with regard to the acceleration of the Moon's mean motion. The other work was a paper by Delaunay on the subject just referred to. Hansen's theory makes the acceleration twice as much as Professor Adams does, and Delaunay some time ago came to the conclusion that Adams is right; but the value thus taken does not satisfy the calculation of the ancient eclipses. M. Delaunay now thinks he has found a cause for the discrepancy-viz., that, for reasons which he gives, the Earth rotates the one-hundredth of a second slower than it did 2,000 years ago. Whether correct or not, everything coming from M. Delaunay is entitled to respect. Mr. Stone has examined the paper, and finds that such a retardation of the Earth's rotation would probably produce the effect of reconciling the observations and theory. At all events, the books are most important contributions, and deserve our special thanks.

The Hon. John William Strutt, B.A.,
Frederick Thomas Hughes, Esq.,

Captain Charles Thomas Kerr, R.N.,

The Rev. Alfred William Deey, M.A., and
Thomas G. Rylands, Esq.,

were balloted for and duly elected Fellows of the Society.

The following papers were read :—

Occultation of 115 Tauri, by Mr. Talmage.

Observations of n Argûs, by Mr. Tebbutt, jun., Windsor, N.S.W. The paper contained a number of comparisons of this star with other stars, all made with the naked eye. The first were in 1854, when ʼn Argûs was inferior to a Centauri, but equal to ß Centauri, and superior to a Crucis. In 1860, ŋ Argûs was less than B Canis Majoris, and about equal to ẞ Canis Minoris, and from that time to the present it had been carefully watched and had rapidly degraded in brightness, being in March 1865 certainly not quite so bright as B.A.C. 3655 or 3688.

Mr. Tebbutt also gave corrected elements of the great Southern Comet of 1865.

Comparison of the Sun's Spots observed at Kew with the Observations of Hofrath Schwabe at Dessau in the year 1865, by Messrs. Warren de la Rue, Balfour Stewart, and B. Loëwy.

At both places the number of new groups observed was 93, the days of observation being 153 at Kew, and 307 at Dessau. At Kew, 13 days were without spots, and 26 at Dessau. The coincidence as to groups recorded showed that none escaped observation at either place.

The President stated that the Kew helio-photographs were taken by Miss Beckley, daughter of the Mechanical Assistant, and that he thought such work peculiarly suitable for ladies.

Note regarding the Decrease of Actinic Effect near the Circumference of the Sun, as shown by the Kew Pictures, by the same Authors.

This decrease is attributed to the effect of a comparatively cold atmosphere, and, in conformity with the authors' views, this atmospheric effect ought to be greater at the epoch of maximum than at that of minimum spot frequency; and furthermore, if there is any reference to ecliptical longitudes in the behaviour of spots-that is to say, if at any time the spots attain their maximum at any ecliptical longitude-there ought to be a greater amount of absorbing atmosphere at the same longitude, since such an atmosphere is supposed conducive to the outbreak of spots.

Mr. B. Stewart has shown that the spots are influenced by planetary positions; and although this is not clear as to Jupiter, it is well marked with regard to Venus, the spots appearing to attain their maximum in the ecliptical longitude opposite to where Venus is so that we might expect a diminution in atmospheric effect in the same longitude as Venus, and an increase in the effect in the longitude opposite to Venus. If, therefore, Venus be at the longitude of the left limb of the Sun, this limb should exhibit less atmospheric effect than the right limb, and vice versa.

Only underexposed pictures can be used for this investigation, as if the plates be exposed long enough to obtain sharp definition of the edge and spots, the physical features of the surface are lost. Mr. Beckley compared the best pictures of 1859, a year of maximum, with those of 1864 and 1865, periods of minimum spot frequency, and he came to the conclusion that there was more atmospheric effect in 1859 than in the other years.

Miss Beckley and Mr. Stewart also examined all the pictures from 1863 to the present time, with reference to the position of Venus, and find the results at least in conformity with the views stated above, while, at the same time, the evidence is not sufficiently strong to establish conclusively the truth of the hypothesis.

Tables of the position of Venus and amount of atmospheric effect at each limb having been given, the authors conclude

1. That when Venus is evidently to the left, there is most atmospheric effect to the right.

2. When she is in conjunction or opposition, there is a tendency to equality.

3. When she is evidently to the right, there is most atmospheric effect to the left.

The President added-All these investigations may be interpreted differently by different persons. What we seek to do is to record faithfully what we find, in the hope that such observations will be useful. It will be remembered that I have endeavoured to photograph the Sun on a scale of 3 ft. diameter, but there are great difficulties with a reflector; and I am happy to say Mr. Cooke has undertaken to make me a refractor of 13 in. aperture, having the visual and actinic foci coincident for this purpose.

Positions and Elements of the Comet discovered at Rome by M. Secchi on the 9th December, by Professor Donati.

The comet was of extreme faintness, and was at first supposed to be Biela's; but in a subsequent letter to the President, Professor Donati announced that it had turned out to be Faye's Comet.

At the request of the President, Mr. Huggins gave an oral account of his observations on Tempel's Comet, which he had communicated to the Royal Society. The comet is an oval nebulous mass, having a minute stellar nucleus. Under prismatic analysis the coma gave a continuous spectrum, while the nucleus point indicated that it was self-luminous, and consisted of gas at a high temperature, like some of the nebula. A continuous spectrum from a self-luminous body indicates that it consists of solid or liquid incandescent matter; but as matter of such extreme tenuity as that constituting the coma of a comet can hardly be solid or liquid, it is probable the light is only that of the Sun reflected to us, and therefore we can draw no conclusion as to its state from the spectrum; and, in the event of this conjecture being well-founded, we may hope, in the case of brighter comets, to recognise some of the solar lines in the spectrum of the light so reflected.

Admiral Manners asked whether the coma might not reflect the light of the nucleus and not that of the sun?

Mr. Huggins replied that the nucleus would be an insufficient source of light; and that as the character of light is not changed by reflection, if the light of the coma came originally from the nucleus, the spectra of both nucleus and coma would be alike, which they were not.

The President wished to know whether we were to consider the coma as probably solid or liquid; at any rate not gaseous?

Mr. Huggins: The spectroscope gives us no information as to the state of matter which simply reflects solar light. If a continuous spectrum result from a self-luminous body, that luminous matter must be solid or liquid; but in the case of this comet, I conclude that the spectrum tells us neither one thing nor the other, as I believe the comet only reflects light, except the nucleus, which displays bright lines like a gaseous nebula.

The President: Mr. Huggins is very cautious in guarding the spectroscope from saying more than he can warrant.

Mr. Pritchard enquired whether there was any doubt that the coma had emanated from the nucleus?

Mr. Huggins: The process generally appears to be, that the nucleus sends out jets of light, which form successive envelopes, and probably cool down sufficiently to take other forms than that

of gas.

Mr. Pritchard congratulated the meeting upon having obtained more definite information as to the nature of comets than they had ever heard before, and remarked that, although others had worked upon the subject of prismatic analysis, Mr. Huggins appeared to have made it his own, and that he proceeded with a caution as rare as it was commendable.

On the Stars within the Trapezium of the Nebula of Orion, by Mr. Huggins.

As prismatic analysis shows this nebula to be gaseous, it is probable that the changes which many observers think are taking place in its form and brightness may lead to the determination of the true cosmical nature of these bodies. The various accounts of minute stars within the trapezium show they are subject to considerable variations. Messrs. Lassell and Otto Struve were quoted to show that the 5th and 6th stars are certainly variable, the 6th having been sometimes seen equally well with the 5th, although, as a general rule, it is decidedly more difficult. On the 8th January, being a remarkably fine night for observation, Mr. Huggins, with his 8-inch refractor, discovered three small stars in the trapezium not before seen, and which he described by aid of a diagram. They were first noticed with a Kellner eye-piece magnifying 60 diameters, and afterwards viewed with double convex lenses giving powers of 135 and 220; the stars being again well observed on the night of January 8th. The first of the three stars (7 in the diagram) was near the centre of the trapezium, and fainter than the well-known 6th star, which on these nights was decidedly inferior to the 5th in magnitude. The next star (8) was near a of the trapezium, and perhaps a shade brighter than No. 7. It can scarcely be one found by M. Porro in 1857, as he places it nearly midway between a and y The star 9 of the diagram was very faint, and only seen by glimpses;

it is probably one seen by De Vico in 1839, but when Mr. Huggins found it he had not seen De Vico's diagram. Neither of the three stars agrees in position with the new star discovered by Mr. Lassell at Malta in 1862. We do not know whether these stars are physically connected with the great nebula, or only optically; but it is important on this point to determine whether the variability of stars and appearance of fresh ones are connected with changes in the nebula itself.

Mr. Huggins further stated that the stars were seen on a dark ground, and not on wisps of the nebula.

Capt. Noble remarked that he had seen the 6th star of the trapezium with his 4.2-inch telescope, and had shown it to others. He always saw the 5th star, but the 6th rarely, and yet Mr. Brodie, by gauging the magnitudes, only found o5 difference. He therefore thought the 6th must be variable.

Mr. Stone remarked that it would be unsafe to infer a star not to be the same as Porro's solely on reference to the diagram in the Monthly Notices, as the engraving sometimes departed slightly from the drawing.

Mr. Huggins said that with regard to seeing the 6th star, it was so near a that unless the atmosphere was so good as to show a without rays the 6th star could not be seen at all.

The President remarked that he thought the whole system variable. Although having other objects in view he had often looked at the trapezium, and sometimes seen both 5 and 6, but at other times neither.

A letter from Commander Ashe to the President, recommending the establishment of a large telescope on one of the Llanos or high plains of the Andes, to observe the discs of the planets and the solar surface, was read. The writer adverted to the success of the Teneriffe expedition, and thought a greater elevation, such as 20,000 feet, would be still more advantageous. The Pass of Tarcora has such an elevation, and can be reached in three days from the city of Tacna, on the Pacific coast. He suggested proceeding to this port, and sending out a party to select a station which could be reached by mules; and as these animals can carry 4 cwt. each, the equatorial could be safely conveyed to the desired spot in pieces. He had even seen a Collard pianoforte carried over the Andes.

Admiral Manners said that for any special purpose such an expedition might be desirable; but unless some peculiar information from a given spot were wanted, he thought the proposal unwarranted, as the Teneriffe expedition had demonstrated the advantage of such situations.

Mr. Evan Hopkins had crossed the Andes five times, and thought the proposed results might be attained without much trouble or expense. Quito, Guayaquil, and Bogota were all at