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nor troublesome, as without it the light from the star might fall at different angles on the prism, which would then produce a different effect. Since P. Secchi's former letter he had found some difference in the measures of some lines, but upon reverting to the original apparatus they appeared unchanged. With regard to the particular band in a Orionis, he had never said there was no such band, but simply that it was not the band which he and Dr. Miller found had faded out.
Results of some Observations of Bright Granules on the Surface of the Sun, with Remarks on the Nature of these Bodies : by Mr. Huggins.
The author justified his employment of the term “bright granules ” in preference to the synonyms used by other observers, on the ground stated by Mr. Dawes, that it involved no hypothesis. His observations were confined to those parts of the solar surface free from the disturbing influence of spots, which occasioned the drawing out, dissipation, and other alterations of the bodies in question. In all other parts, within certain limits, they have a degree of permanence in shape. Mr. Huggins considered: 1. Their distribution. With the exception above stated they are found all over the sun's surface, and occasionally preserve their normal character on the penumbra of spots. Once he fairly resolved a facula into granules, with a few detached particles round the edge. 2. Form. With powers of about 100 no comparison is so good as that of "rice grains," but with higher powers this uniformity disappears, and they become very irregular and broken in outline. Disregarding this, they may be called generally oval. They appear not to be flat disks, but of considerable thickness, and if viewed from the sun would doubtless be as rugged in outline as our clouds. 3. Size. On March 26, the sun's image was passed over the wires of the micrometer 2':59 apart, when two of the granules generally filled up that space,
The longest diameter was therefore about 1".5. In some areas the groups were nearly alike in size, but in other parts the granules were smaller, with a few very large. 4. Mode of grouping. The granules are congregated in patches, closely united into oval clouds like masses, or sometimes in long bands. On April 26 there was a long oval border of a tesselated nature, where the granules were sparsely exhibited. A diagram collecting the results of numerous days' work was shown. The coarse mottling of the sun is produced by this mode of aggregation, another cause being the difference of brightness due to the different levels of the surface, forming corrugations or waves in the photosphere. Mr. H. was not able to satisfy himself as to the nature of the darker portion of the surface, but is convinced the granules give out the greater part of the light, and thinks they are not superposed, but appear to sink down through a medium, as Sir J. Herschel has well described. 5. Nature. After many years' experience, Mr. Dawes thinks the various forms are only different conditions of surface. The author differed from this view only so far as to suggest that the granules were originally separate clouds, which soon unite with the surface beneath them. The spectroscope suggests that some explanation may be found in the different powers of radiation, and other forces possessed by the various parts of the surface. Mr. Balfour Stewart's Law of Exchanges was also referred to, but the author thought the difference between the dark pores and the bright granules was not yet explained. The notion of a downward rush of gas at the spots does not apply to these smaller dark points.
Mr. Huggins added orally that he had been endeavouring to see whether the larger diameter of the granules coincided with the direction of the currents detected by Mr. Carrington, but he had not yet obtained any definite result. He had tried polarisation for reducing the sun's light, and found a good effect from using his prism with a tourmaline, when a very light glass shade was all that was then required, only about one-fifth of the light remaining unquenched. This was with the prism at 45°; but when placed at the proper polarising angle for crown glass, 50°45, nearly all the light was absorbed. Light of different refrangibilities was not polarised at the same angle, for all rays
and little colour might therefore be left outstanding, as, if adjusted for the green, the red and blue would be left.
This would probably explain the red patches on a spot seen by Secchi with his polarising eye-piece.
Mr. Stone was greatly pleased that observers were getting so close together on the subject of the solar photosphere. He preferred the term “ willow leaves to all others, as there was a manifest tendency to elongation. He believed the surface was broken up into patches of granules, having a strong tendency to a long form, and that these played an important part in the physics of the sun; and we owed a debt of gratitude to Mr. Nasmyth, who first drew attention to their existence.
Mr. Hodgson inquired the aperture, power, and focal length of Mr. Huggins's telescope.
Mr. Huggins : Eight inches aperture, jo feet focal length. The powers, generally, 100 to 600. The drawing, seen at a distance, represents the sun with about 300. With 100 the granules are seen, but not in detail.
Mr. De la Rue said it was satisfactory that all observers were agreed on there being elongated forms, and he could well understand that in times of inferior atmosphere and impaired definition, the middle of these bodies would be seen better
than the extremities and other forms thus described. It required the finest atmosphere and best definition to see the willow leaves, and to distinguish them from thatch 'granules’and other markings. He congratulated Mr. Huggins and other observers on the success of their labours.
Mr. Hodgson had come to the same conclusion as Mr. Huggins with respect to the cause of Professor Secchi's red spots. They were doubtless a residuum of unpolarised light, and although seen only at one part, might probably have been detected in others as a fringe of colour, if looked for.
Mr. Brayley said one observation had not been alluded to yet, namely, that faculæ had been seen sailing over the umbra of a spot. Mr. Huggins had seen granules in this position, which agreed with Herschel's description of the photosphere and atmosphere of the sun. In the four forms of bodies described in a letter of Mr. Nasmyth, read at a former meeting, two agreed with the account of the granules-the willow leaves being more rarely seen. Mr. Huggins's view that these bodies were solid, and yet cloudy, undergoing dissolution into fluid and vaporous matter, agreed with that entertained by Chacornac, and the speaker's account in his first paper in the “ Companion to the Almanac."
In the application of terrestrial physics to solar phenomena, we must bear in mind that the relations of solidity, liquidity, and gaseity there, must be very different to their types here. In the sun they would pass so rapidly from one to the other as to differ only differentially, as it might be called. Graham's new views on the states of matter had an important bearing on this point; and Sir J. Herschel, in a paper in the
Quarterly Journal of Science,” had suggested that the Cagniard de la Tour state of matter, when liquids take the aeriform state without change of bulk, must be borne in mind. tion of matter on the sun must be intensely different to that on the earth.
On the Satellite of Sirius : by M. Otto Struve.
Before reading this paper, Mr. Stone gave an account of the prior researches on this subject. In 1844, Bessel pointed out that the irregularities in the proper motion of Sirius might be due to the presence of a non-luminous body. In 1851, Peters calculated an elliptic orbit for the star and its supposed companion, which in 1861 was extended by Safford from positions in R.A. which had only been computed by Peters to those in declination also, and he showed that the same orbit would account for both. Auwers also had investigated the subject. In 1862, Alvan Clarke detected a small star near Sirius, which was afterwards observed by Bond, Dawes, Lassell, Struve, Marth, and others, and its position was found to agree well with the
forms of the theoretical ellipse. It has been carefully observed by Struve in 1863-4-5-6, who has proved it is in physical connection with Sirius; but the idea that it is really the disturbing body has yet to be established.
In the paper read, M. Struve said that he formerly thought the small star did not partake of the proper motion of Sirius, and indicated his reasons, but suspending his opinion. After two years' further observation he was better able to discuss the subject. His observations were very numerous, and of both distance and . position angle, the measures being corrected as to the angles for a small error deduced from observations on double stars. The 1865 observations were made at Rome, the rest at Pulkowa. The measures were given, and it was shown that, had the star been only optically double, the angle would have changed largely, but it had not, and he therefore considered its connection proved; and as the micrometrical measures agreed well with Auwers' results, we could hardly doubt that Alvan Clarke's comes was the disturbing body. Admitting this, its mass must be very large--at least one-half of that of Sirius itself; and if of like constitution, it should have been a star of the first magnitude, whereas it was only of the ninth. It must therefore be of very different constitution, and the light was not increasing, as the author once thought.
Mr. De la Rue: This investigation promises to mark a very important era in sidereal astronomy, as it is probable other irregular proper motions may be referred to disturbing bodies. We can hardiy in such a matter expect a closer agreement between theory and observation.
Mr. Stone : Theory requires a change of about 8° in position, and observation differs little from this amount, but proper
motion alone would alter the angle 15°, so that the stars must be a physical pair. The difficulty is from the small magnitude and large
There has been a paper in the Ast. Nach. lately, arriving at the same result.
Mr. De la Rue: Position angles are at all times difficult to measure, but especially with so bright a star near the faint one.
Mr. Marth: There ought not even then to be an error of more than 2°. M. Goldschmidt has given a diagram of several small stars seen near Sirius with a small telescope, but I have never seen them with large instruments. Once, at Malta, with Mr. Lassell's, I suspected one half-way between Sirius and the comes, but the observation could not be verified afterwards.
Mr. Stone called attention to a difficulty as to the variable star x Cygni. The star lettered
is smaller than one near, not so distinguished by Bayer, and this latter has in most catalogues had its place given instead of that of the true x. Mr. Stone suggested that they should be called x' and x2 in future.
[With regard to the last paragraph in our report of the meeting of April 13, Mr. Brothers requests us to state that it was only intended to take four pictures on a plate the size of that exhibited, but by having a succession of frames, with plates ready prepared (one after the other, in quick succession), 30 pictures of such a phenomenon as a solar eclipse might be obtained, assuming that the exposure required would be short ; but of the total phase, as 153 would generally be required, it would not be possible to do more than 10 or 12. Of a total eclipse of the Moon, 100 negatives might be made.]
THE NEW VARIABLE STAR.
On the 16th May, Mr. Huggins received a letter from Mr. Bermingham, of Tuam, announcing the discovery, on the 12th, of a new star in Corona Borealis, of the second magnitude. On the same day, a little later, Mr. Huggins had another letter from Mr. Baxendell, stating that he had seen the star on the 14th, when it was of the third magnitude. Mr. Huggins wrote to the Astronomer Royal and others on the subject, and himself observed the spectrum of the star the same evening. The result is most remarkable. The star has two spectra, one superposed on the other. One spectrum has the colours and dark lines usual with fixed stars, and showing their analogy to our Sun; while the other consists of five bright lines, two of which the brightest) are identical with C and F of the solar spectrum, and indicate hydrogen, with which they have been directly compared. This gas, in large quantity, and at an extremely high temperature, must (with other gases) surround the photosphere of the star; and such phenomena naturally give rise to much speculation on the extraordinary state of things existing there, and producing the sudden blazing up of the object. The Astronomer Royal has made meridian observations of the star, and thinks it may not be an entirely new one, but probably a star catalogued by Argelander as of 95 magnitude. This interesting object has now diminished below the sixth magnitude; its position, as given by Mr. Baxendell, is R.A. 152. 53m. 278.; Decl. + 26° 20'.
Mr. Hind writes to the Times :-"Having received information this evening through the kindness of Mr. W. Huggins, F.R.S., that a new star in the constellation Corona Borealis had been discovered by Mr. Bermingham, of Tuam, and Mr. Baxendell, of Manchester, we found it without difficulty, though its brightness has evidently diminished with great rapidity since the earlier observations, when its light was equal to that of an ordinary star of the second magnitude. The mean position for 1866 was determined with the equa- toreal, and is as follows: Right Ascension
15h. 53m. 53'05. North Polar distance