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Cambridge to pay the last tribute of respect to his friend's remains to-morrow. Mr. Cayley also was absent on the same account.
Upon the suggestion of Mr. Mummery, the step taken by the Council was ordered to be referred to in the minutes.
The minutes of the last ordinary meeting were read and confirmed, and
Fifty-nine presents were announced.
J. Mathieson, Esq.,
H. Dodgson, Esq., M.D.,
The following papers were read :
On the Investigation of Cometary Orbits : by Professor Hoek, of Utrecht.
This was an addition to the author's previous papers on the same subject, and explained how he had discussed the orbits of 190 comets, appearing since 1536, by drawing their paths and noticing where the aphelia were distributed. Circles of 10° in diameter were drawn round these points, and the intersections gave
indications of the directions in which the sources of each system were to be sought. Several of these intersections were pointed out and examined in detail.
The President said that M. Hoek's theory appeared to be something of this sort : Comets appear from to time, and are then associated with our system; but they may at other times have been connected with other stars or suns, and have been drawn
away from such particular star or sun, and out of its sphere of attraction, into that of another star. Can we make out the particular stars or suns with which our comets have at certain times been associated ? M. Hoek thinks he has found that at one period or another some of the comets appearing to us have belonged to other suns and systems, and he believes he has brought this to a mathematical deduction. This may turn out to be a beautiful law, and account for the present non-appearance of Biela’s Comet, which we have before seen become dichotomized, and which may now have gone to join another system.
On Airy's Double Image Micrometer : by Professor Kaiser, of Leyden.
The Author stated that, at the request of Mr. Main, he had forwarded the results of his investigations of this valuable instru
ment. For the details of its construction and theory he referred to Mr. Airy's papers, and stated that in 1855, having had one made for his 6-inch refractor, he had carefully examined its capabilities. He found it liable to three kinds of error : 1. Periodical errors of the screw ; 2. Variability in the mutual distances of the threads of the screw ; and 3. Distortion of the images. In the instrument made for him by Mr. Simms, one semi-lens only was moveable, which prevented the elimination of the first error directly, and he recommended that both halves should be moveable, which would also enable larger angles to be measured. He had, however, determined the periodical errors by a circuitous process,
gave results showing that the error was large. As this micrometer renders important service to astronomy, effecting results comparable with those of a heliometer, and as it is always used with a fine refractor, he thought some little additional expense should not be spared to make it perfect.
Mr. W. Simms, in answer to the President, said that, before adverting to the Professor's suggestions, it would be necessary to read them carefully in extenso. So far as making each semilens to move, that could be easily done, but it would not enlarge the field. The optical construction of the micrometer prevented this. The alteration would only give the power of using another part of the screw.
The President: When the paper has been printed, Mr. Simms will no doubt turn his attention to the subject, and give us his views thereon.
Mr. Stone said he could well enter into the difficulty which a theoretical inventor had in getting his ideas carried out, and how small instrumental errors perplexed an observer. In illustration of these unexpected troublesome matters, he mentioned that it seemed probable, in the Greenwich instruments, the wires, instead of being horizontal, took a curved form, and thus gave a North Polar Distance greater with the last wire than the centre, and that a correction might become necessary for this deflection.
On a Scorpii : by Mr. Freeman, of Mentone.
The Author stated that he had seen the companion of Antares with a power of 180 on his 43-inch refractor. * He thought it singular that the small star had only recently been discovered ; but probably, the latitude being more favourable than that of England, made it easier at Mentone.
Capt. Noble said he had often seen the companion here.
Mr. Talmage stated that 3 miles from Mentone he had observed the star with 3 inches aperture.
Mr. Hodgson : It is simply a question of atmosphere.
* See Ast. Reg. No. 39, p. 82.
On the Path of a Detonating Meteor : by Mr. Alex. Herschel.
This communication related to the meteor seen by Mr. De la Rue and others on 21st of November last, and was nearly identical with Mr. Herschel's letter in the last number of the Astronomical Register, p. 80.
Capt. Noble asked how the times mentioned in the paper were ascertained? The appearance of meteors was so sudden, that the observer was generally too much startled to look immediately for the time, and the watches in general use varied too much to allow of comparisons depending on a few seconds.
The President: Mr. De la Rue is known to carry a beautiful chronometer, and is not likely to be mistaken.
Capt. Noble : But others do not.
Mr. Lockyer : Mr. Penrose, of Wimbledon, is also an excellent observer, and has a good watch.
The President: I never read any of these papers of Mr. Herschel without being carried away, I know not where. They show how we are groping after the truth. Thanks to Mr. Huggins, we are now comparing the matter of stars with our sun, and that of comets with nebulæ; while, with M. Hoek, we are looking whether comets are connected with certain systems for a time, and then attached to others. All at present may be chaotic, but order and beauty must be the result; and we should be deeply thankful to those who work on such subjects, and pass sleepless nights watching for materials to evolve the truth. “As to the particular subject of meteors, the observers whose observations are relied on for the results are on the look-out for the very things, and are therefore not so much taken by surprise, and are, of course, provided with good time-keepers:
On the Identification of Sir Wm. Herschel's Double Stars, and a Copy of all his diicrometrical Measurements of them: by Sir John Herschel
The President: The history of the paper is this:-Some time ago I had occasion to go to Collingwood, when Sir John put this Catalogue of all his father's double-star measures into my hands for the Astronomical Society. The Council were in hopes of inducing Sir John Herschel to write an introduction to the Catalogue, when it would appear in the memoirs, and form a worthy companion legacy to his Catalogue of Clusters and Nebulæ, recently printed by the Royal Society.
Mr. Chambers inquired whether any information had been obtained with respect to Biela's Comet ?
Mr. Talmage said that on the 17th of December he had found a very
faint object with Mr. Barclay's 10-inch refractor, not far from the predicted place; but he could not find it again, nor was any nebula known to be in the position where he had seen the object.
The President hoped that a proper record of the observation would be made.
Mr. Talmage said he sent the corrected position to Mr. Hind by the next post, and would also communicate the observation to the Society if desired, that it might be taken for as much as it was worth.
Mr. Chambers : Secchi has sought diligently for the comet, and thinks he could not have missed it, had it appeared.
Mr. Buckingham : I saw it on the oth of November, with my refractor of 20 inches aperture. It was a long way from the place given by the ephemeris—as much as 10°, I think-and very
faint. I could not see it at all with
I ascertained it was in motion, and compared it with stars.
The President: Do you mean that you measured the differences in position with respect to stars on the same night?
Mr. Buckingham : I only made one observation with two wires, having no micrometer or illumination of the field.
The President requested Mr. Buckingham to put his observations also into writing for the Society.
Mr. Stone : Did you watch for any length of time?
Mr. Buckingham : About half an hour; but I only got one position.
Mr. Talmage: At Pulkowa, where they have a large glass, the twilight is probably too great for the comet to have been I very
much doubt whether its motion would be perceptible in half an hour, the want of a definite point for measuring from making a difficulty.
On the New Star of the Year 393 B.C. : by M. Herman Goldschmidt.
This paper was an attempt to prove the identity of this star with others seen in 1203, 1609, and 1827, and that it was therefore a variable of long period. In answer to the President,
Mr. Chambers thought it likely that several of the temporary stars would turn out to be long-period variables, and he had included one or two of them in his Catalogue.
On the Spectrum of a Orionis, with a drawing; and on a Drawing of a Sun Spot: by P. Secchi.
The Author remarked that the details of the spectrum were strange and wonderful, though the prism was small. The double line of sodium and the magnesium lines were used as points of reference. There was a difference in the nebulous bands as compared with those of other observers, and he suggested that a change was possible. Sirius had
. a wonderful spectrum, full of bands, like the spectrum of sulphur in Plücker's drawings. Rigel also had similar bands, but narrower, like those of nitrogen in Plücker's plate. In the
drawing of the sun-spot there were some red patches, only seen with a polarising eye-piece, and disappearing with all others.
Mr. Huggins, being called on by the President, said he would prefer postponing his remarks until he could consider the
paper and examine the spectrum more carefully, and write what he had to say on it. He would just observe that it was not stated how the measures were made, nor how many lines had actually been measured. With regard to change, he had lately remeasured some of the groups of lines, and found no symptoms of change in them. The colours indicated for the various parts of the spectrum in the drawing did not correspond with those existing where the principal lines referred to were situated. As to Rigel and Sirius, Rutherford and the early observers saw no fine lines in these spectra, but only 3 or 4 broad bands in the red, green, and blue; but Dr. Miller and the speaker, with improved instrumental means, found the spectra of these stars furrowed with fine lines, and observed the probable coincidence of some of them with the double D, and the triple b. The lines of these stars did not appear like the spectra of sulphur and nitrogen referred to in P. Secchi's letter. As to the red patches on the sun-spot, Mr. Huggins believed it was the first time they had been seen on the umbra.—The drawing represents a large spot, with penumbra, umbra and nucleus, and the red portions are on the umbra. Secchi says no more in his letter ; but in a recent number of Les Mondes he appears to connect the phenomenon with the red prominences seen in eclipses. He appears to think he has here seen the rosecoloured prominences projected on a dark spot. He uses a new eye-piece made by Merz, consisting of 4 plane mirrors of black glass placed in the axis of the telescope. If anyone present has seen the red prominences, he will perhaps be able to say whether they are likely to be visible under such circumstances.
Mr. Lockyer said that the large spot recently described by Mr. Howlett had the umbra copper-coloured and violet at times. He (Mr. L.) used a diagonal glass reflector and the usual negative eye-piece.
Mr. Hodgson mentioned that M. Porro, at Paris, placed the diagonal glass reflector at the proper polarising angle, and then, with a 25-inch silvered glass speculum, could look at the sun without a dark glass.
The President observed that it required a second reflector to produce polarisation, so as to take off the light. This Merz evidently uses, and then any modification from full illumination to darkness can be obtained. He had himself seen the red flames of total solar eclipses, and could say that they had light enough to be visible just before and for a few moments after totality; so that they bear a tolerable amount of light. He