the solar spots with a spectroscope specially prepared for the purpose by Mr. Browning.

The last-named gentleman is also preparing a powerful spectroscope for use with the great Parsonstown reflector. The Earl of Rosse, following worthily in the footsteps of his father, is about to apply the unrivalled light-gathering powers of this instrument to the spectroscopic analysis of objects too faint to be reached by smaller telescopes. Clockwork is to be so applied to the great telescope, so that it will follow stars and nebulæ as closely as a smaller equatorial would.

Our readers will be glad to hear that the instruments supplied by the Royal Society to the expedition under Lieutenant John Herschel have already been applied to useful work-six nebula in the southern hemisphere have been examined with the spectroscope. The great nebula in Argo is found to exhibit a spectrum of bright lines, so that, like its rival in splendour the great Orion nebula, this object is gaseous.

The great eclipse of August 17th will be well watched. Besides the expeditions sent out under Lieutenant Herschel and Major Tennant, there is to be one under the charge of Mr. Pogson, the Government astronomer at Madras; another has been sent out by France under M. Jansen; the Papal government sends out Father Secchi, and there is also to be a Prussian expedition. Mr. Huggins has sent out to Mr. Pogson a spectroscope and apparatus for observing polarization.

The Minister of Public Instruction in France has lately submitted to the Council of State the draft of a decree for the complete reorganization of the Imperial Observatory at Paris. It is stated that this establishment will be removed from its present site, which is very unfavourable for astronomical observation, owing to the vibration of the building caused by passing vehicles. The air also in the neighbourhood of the Observatory is so heavily loaded with smoke and vapour as to interfere with many of the delicate observations which have to be made by astronomers of the present day. We learn that owing to these causes it is impossible to apply a higher power than 500 to the great equatorial. It is proposed to remove the Observatory to Fontenoy-aux-Roses, south-west of Paris.

The planet Venus is now very favourably situated for observation. She has been seen several times in full day-light. Mr. Browning has observed several faint markings on the planet, resembling the grey plains on the moon. "These markings seem to be studded with white spots of various sizes." It is a pity that modern astronomers do not make an effort to learn something respecting the axial position of Venus. Large achromatics do not seem well suited to this work, on account of the extreme brilliancy of Venus.

Reflectors used with a solar eye-piece containing a simple surfacereflecting prism, seem to give the most satisfactory views.

The ninety-eighth asteriod was discovered by Mr. Peters, at Clinton, on April 18th last; it is of the twelfth magnitude.

The lunar crater Linné continues to be a subject of dispute in the astronomical world: the opinion is gaining ground that there has been no change in the crater, but that, owing to the peculiar character of the moon's surface in this neighbourhood, very slight variations in the illumination serve to produce marked variations in the appearance of the crater. At a late meeting of the Astronomical Society, Captain Noble stated that a "few hours sufficed to change a distinct ring into a smudge."

Saturn is now an interesting object of observation, though his southern declination is unfavourable to distinctness. His rings are well open, the outer edge very nearly coincident (in appearance) with the outline of the ball. It is to be hoped that something may be learned respecting the structure of the rings during the present and the next two oppositions, as some fourteen or fifteen years will elapse before the rings are again opened to their full extent.

PROCEEDINGS OF THE ROYAL ASTRONOMICAL SOCIETY.

M. Hoek, director of the Observatory of Utrecht, remarks on the small distance which separates the intersection of the orbits of comets III. and V., 1857, from the point which he has assigned as the radiant point of cometary orbits. Comet III., 1867, unexpectedly confirms his views, since, as we have mentioned in a former Chronicle, the circle which is the intersection of its orbit-plane with the celestial sphere passes through almost the same point of the sky. Thus, he adds, "the last ten years have furnished us with two Cometary systems, each composed of three members; first, that of the years 1860 and 1863, then that of the years 1857 and 1867. It appears that it would be to mistake the principles of the theory of probabilities, if we attributed all these coincidences to mere chance."

He supplies also an elaborate memoir on the phenomena which a very extended swarm of meteors, coming from space, would present after its entry into the solar system. He takes the case of a swarm of corpuscles coming from the stellar spaces, and sufficiently extended to embrace the whole earth. It would be impossible in the space available to us to give even a sketch of the processes applied by M. Hoek, which occupy no less than eighteen pages of calculation. Some of the results at which he arrives agree closely with those lately published by M. Schiaparelli, in a memoir entitled "Note e Riflessioni intorno alla Teoria Astronomica delle stelle cadenti." M. Hoek finds that under certain circumstances, the earth's attrac

tion may have the effect of shifting the radiant point more than 17°. In future therefore it will be necessary to note the hour and the minute of each observation made on a falling star.

Sir John Herschel has been engaged, since he sent to the Astronomical Society his synoptic catalogue of stars observed by Sir William Herschel, in forming a general digest of all the recorded measures of all known double stars-a task which "he hopes to leave in such a state of forwardness as will ensure its completion by some other hand." While engaged on this task, he has been led by the coincidence, or near coincidence, of the measures taken by Sir William with those of stars observed by others, to the identification, more or less probable, of a considerable number of these stars with those subsequently measured. He supplies a list of the objects in question, judging "that information of this kind cannot but prove interesting to observers engaged in the measurement of double stars." In the progress of the work he has been led to the detection of a somewhat formidable list of errata in the printed catalogue. We should recommend those who possess or make use of the catalogue to pay attention to these errata, some of which are important, and, if uncorrected, likely to cause the observer considerable waste of time.

Mr. Key supplies an interesting paper on the planetary nebula 45 H Geminorum. This nebula was discovered by Sir W. Herschel in 1787, and is described by him as "a star of the ninth magnitude, with a pretty bright nebulosity equally dispersed all round." The younger Herschel describes it as "a star of the eighth magnitude, exactly in the centre of an exactly round bright hemisphere 25" in diameter." Lord Rosse gives an account of the same object in the 'Philosophical Transactions,' 1850. He saw it as a nebulous star with a black patch close to it on the preceding side, a less luminous space somewhat unequal in breadth surrounding the nucleus, and a luminous ring at some distance; this ring being of less breadth on the following side. Mr. Lassell's drawing of the object, in 1862, represents a star in the centre of a planetary disc, surrounded by a nonluminous space, and, at some distance, by a luminous ring of considerable breadth. He adds that "he can see no trace of the dark patch of Lord Rosse's drawing near the bright centre." Mr. Key, using an 18-inch silvered-glass reflector 10 feet in focal length (of his own make), finds the present appearance of the object to be different. It appears as a bright but somewhat nebulous star, closely surrounded by a dark ring; this again is surrounded by a luminous ring; then comes an interval much less luminous, and finally, at some distance, an exterior luminous ring. The whole is almost exactly symmetrical, though not quite so; the dark space between the two bright rings being darker on the north following side, and the preceding side of the whole object is rather fainter than the rest. Of the two luminous rings the inner is considerably the brighter.

Mr. Key considers that there is a progressive character in the results above recorded, since the various aspects of the nebula do not appear to depend on the power employed. His own reflector is somewhat more powerful than the Herschelian 20-feet reflector, but is of incomparably inferior power to the instruments of Lord Rosse and Mr. Lassell. "One fact," he adds, "seems, at all events, abundantly evident, viz. that whereas at the date of the Herschels' observation, there was no appearance whatever of a ring surrounding the central star, at the present time there are two."

Mr. Simms supplies a description of a zenith telescope employed in America, and explains a method of determining the latitude which has been for several years adopted by the United States coast surveyors, and which has the advantage of being at once simple and exceedingly accurate. The instrument is further described, and figured in a later number of the Society's notices, in a paper by Mr. Davidson, of Germantown, Pennsylvania. The method of observation, known as Talcott's, is worth studying:"Two stars are selected, one of which passes the meridian to the north, and the other at nearly the same distance to the south of the zenith. The telescope is brought into the plane of the meridian, and set for the star which first passes the meridian; when visible it is bisected by the micrometer wire, the tangent screw of the instrument being used. The telescope is then turned 180° in azimuth, and when the second star makes its appearance, should there be any difference in the zenith distances, this distance is measured by the micrometer screw." The latitude is readily deduced. For example, suppose the polar distances of the two stars are D and D' (D less than D'), and that the former star, when on the meridian, has a zenith distance less than the corresponding zenith distance of the other by a small arc d; then a star, whose polar distance was D-d, would cross the meridian at exactly the same altitude towards the north, as the star whose polar distance is D' has towards the south. Hence the polar distance of the zenith of the place of observation, that is, the complement of the latitude, is (D-d\+ D'). Mr. Davidson says that, after twenty-two years' experience in using prime vertical transits, vertical circles, and Airy's zenith sector, he can affirm confidently that the zenith sector of the coast survey, used as above described, is far better than any of them.

Father Secchi supplies an interesting paper on the great nebula in Orion. He has also sent to the Astronomical Society a drawing of the nebula, commenced several years ago, and finished last year by combined observations made by himself and Father Ferrani, his assistant. One point in Father Secchi's paper will excite surprise. He states that the nebula is much better seen in moonlight than on dark nights. He considers that this is a consequence of that optical principle, that the difference of two lights is more easily

appreciated when they are weak than when both are strong. He finds that, as Mr. Huggins had anticipated, the spectrum of hydrogen may be made, by sufficiently diminishing the light, to present the middle line only, which is that visible in the nebula.

Mr. Stone supplies a valuable paper on the rejection of discordant observations. His theory is that the rejection of such observations cannot be made except upon a direct admission of carelessness on the part of the observer; and he shows how the amount of error which justifies a rejection is to be calculated from an estimate of the average number of mistakes made by the observer in a given number of observations.

Mr. Chambers supplies a catalogue of binary stars formed (in the main) by reducing to the year 1870 the stars in the excellent catalogue presented by Mr. A. Brothers, to the Manchester Literary and Philosophical Society.

Mr. Proctor puts forward a proposal for a new star-atlas. The advantages of the plan appear to be the following:-The stars would be presented in a moderate number (12) of maps, uniform in size, shape, and mode of projection; with scarcely appreciable distortion and scale-variation; not too large for convenient use (about 12 inches in diameter), and yet on the sufficiently large scale of an 18-inch globe. The twelve maps would correspond to the twelve pentagonal maps of his gnomonic set, but being made circular and thus overlapping, the connection between the different maps would be conveniently exhibited,

We must leave to our next number the review of several interesting papers which appear in the latest number of the Society's Proceedings. The issue of this number having been delayed for the completion of a lithograph, illustrating Mr. Abbott's paper on certain variations in the nebula surrounding Argûs, we have received the number too late for discussion here. But we are glad to notice that there now occurs less delay than took place some few months ago in the issue of the Society's notices.

4. BOTANY AND VEGETABLE PHYSIOLOGY. Green Rotten Wood.-We have received the following from Mr. H. C. Sorby, F.R.S.:-"In the last number of your Journal (p. 222) you call attention to the colour of green rotten wood, and ask whether it has any relation to the Phycocyan of Cohn. I have examined it carefully, and find it is quite distinct from that or any other colouring matter with which I am acquainted. The chief constituent is a green-blue colour, insoluble in water and only sparingly soluble in alcohol or benzole, and not fluorescent; whereas Phycocyan is soluble in water and very fluorescent. The spectra are