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subjects, less practical in their character, which have also received some attention from men of science, and are likely to be still further pursued during the present year.

The large increase in the number of private astronomical observatories is doing much to extend our knowledge of celestial objects and to accumulate data, the value of which will be fully recognised by future observers. Four more planets have been discovered, and the same number of comets. Of the four planets, three were first observed in Mr. Bishop's observatory,--two by Mr. Hind and one by Mr. Maith. The fourth was discovered by Mr. Luther, at the observatory of Bilk, near Dusseldorf. The four comets are new to us, if not to our system, for they cannot be identified with any that have been before observed. One was observed at Berlin, two at Gottingen, and the fourth was visible to the naked eye in many parts of Europe, and was, on one occasion, seen in daylight by Mr. Hartnup.

The progress of Stellar astronomy keeps pace with the onward march of discovery in the solar system. The erection of Bessel's noble telescope, and the results obtained with it by that lamented astronomer (of which the measure of the parallax of 61 Cygni was the most important), inaugurated a new era.

A large amount of the labour of the astronomers of the two last centuries, long comparatively useless, is now being reduced and catalogued. In some instances this has been already partially done, but much still remains to be done. The British Association volunteered to assist in the accomplishment of the task, and in 1815, published a catalogue of eight thousand three hundred and seventy-seven stars. This catalogue includes many stars of the seventh magnitude; but as these are often calculated from one observation, chiefly by Laland and Lacaille, they are not uniformly correct. In spite of this, however, although the astronomer does sometimes turn his telescope to the point indicated and does not find the star;—and although the place of a star employed as a point of reference for some moving body is not always correctly defined ;-the catalogue is valuable, and the errors will be surely, though slowly, corrected. The detection of error is also an excitement to improvement, and the importance of making another attempt to supply the wants of the astronomer is already acknowledged :

* The British Association would add greatly to the benefits it has already conferred on astronomical science,' says Professor Challis, ' by promoting the publication, when sufficient materials can be collected, of a general catalogue of all stars to the ninth magnitude inclusive, which have been repeatedly observed with meridian instruments. The modern sources at present available for such a work are the reduced and published observations of the Grecnwich, Puikowa, Edinburghi,

N.S. -VOL. IX.

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Oxford, and Cambridge Observatories, and the recently completed catalogue of twelve thousand stars observed and reduced by the indefatigable astronomer of Hamburgh, Mr. Charles Rumker, together with numerous incidental determinations of the places of comparison stars in the - Astronomische Nachrichten.' To complete the present account of the state of Stellar astronomy, mention should be made of two volumes recently published by Mr. Cooper, containing the approximate places arranged in order of right ascension of thirty thousand one hundred and eighty-six elliptic stars from the ninth to the twelfth magnitude, of which a very small number had been previously observed. The observations were made with the Makree equatorial, and have been printed at the expense of her Majesty's government.'

We cannot mention the subject of astronomy without a particular reference to the application of electricity to the duties of the astronomical observatory. Telegraphs, signal balls, and sympathetic clocks, are now to be classed among the common things, and their operations are understood by all intelligent men who watch the progress of discovery and its influence upon society. But it may not be generally known that in no scientific pursuit or commercial enterprise is the voltaic battery more useful than in an astronomical observatory. There is something apparently fabulous, or it certainly would have been so designated a few years ago, in the statement that an electric clock in Greenwich Observatory ‘maintains in sympathetic movement the large clock at the entrance gate, two other clocks in the Observatory, and a clock at the London-bridge Terminus of the South-eastern Railway:-it sends galvanic signals every day along all the principal railways diverging from London -it drops the Greenwich ball, and the ball on the offices of the Electric Telegraph Company in the Strand, and the correctness of the last of these operations is tested by means of a galvanic signal needle upon the case of the Greenwich transit clock. All these effects are produced without sensible error of time. A time-signal ball at Deal has also been connected with the electric arrangement at Greenwich, and thus the shipping in the Downs is provided with the means of obtaining correct time.

Public attention was sometimes since drawn to an ingenious method of determining the difference of longitude between distant places by voltaic signals, invented and used in America. By this method the Astronomer Royal has determined the difference of longitude between Greenwich and the Observatories of Cambridge, Edinburgh, and Brussels ; and in the same manner Professor Encke has obtained the difference of longitude between Berlin and Frankfort-on-the-Maine. As soon as the necessary connexions and turntables had been made for a branch line of voltaic wires from Greenwich Observatory to London-bridge, and those preliminary operations which are necessary to give facility of manipulation were completed, experiments were commenced to determine the difference of longitude between the Observatories of Greenwich and Cambridge. This was the first application of the method in England. In operations of this kind two persons are required at each station. One is the signal giver, who, while observing the transit of stars over the wires of the transit circle with his eye applied to the telescope, completes the voltaic circuit with his finger. The other is the signal observer, and his duty is to watch the motion of the needles and record the time; and at Greenwich this may be done with the greatest accuracy, for the galvanic needle is carried by the transit clock. The order of operation is described by the Astronomer Royal in the following passage:

At 11 P.M. Greenwich mean solar time, Greenwich commenced by giving five signals at intervals of about 2" each. The turnplates were changed, and Cambridge responded by five similar signals. These were merely to say “ all is right.' Then Greenwich gave batches of signals in numbers of from three to nine (some of them being transits of stars) to 11h 15". Then Cambridge gave similar batches to 11h 30m. Then Greenwich gave signals to 11h 45", and Cambridge to 12h 0". This closed the night's signals. From one hundred and thirty-five to one hundred and fifty efficient signals were given, and as the observation of a signal is perhaps rather less accurate than the observation of a transit wire, the probable error of the mean of these will be fairly comparable with that of the determination of clock error in an evening's transits.'

The long disputed question of the origin of the spots on the sun is again revived, and we may now hope to have it settled at no very distant period ; or if this cannot be at once done, we shall at least ascertain if any, and what, connexion exists between their changed form and place and certain physical phenomena with which they are supposed to have some unknown relation. The Kew committee purpose to take a daily image of the sun by the aid of photography, and arrangements are being made for that purpose at the Meteorological Observatory under the advice of Sir John Herschel. Speaking generally of the arrangement, it may be said to consist of a telescope mounted equatorially with a clock motion in parallel ; but Herschel himself will describe, in the following passage, the object proposed, and the means by which it is to be obtained

• The image to be impressed on the paper (or collodionized glass) should be formed not in the focus of the object lens, but in that of the eye lens drawn out somewhat beyond the proper situation for distinct vision, and always to the same invariable distance, to insure an equally magnified image on each day. By this arrangement a considerably magnified image of the sun, and also of any system of wires in the


focus of the object glass, may be thrown upon the focusing glass of a camera box, adjusted to the eye end of the telescope. By employing a system of spider lines parallel and perpendicular to the diurnal motion, and so disposed as to divide the field of view into squares, say of five minutes in the side, the central one crossing the sun's centre (or rather as liable to no uncertainty, one of them being a tangent to its lower or upper limb), the place of each spot on the surface is, ipso facto, mapped down in reference to the parallel and declination circle, and its distance from the border, and its size, measurable on a fixed scale. If large spots are to be photographed, specially with a view to the delineation of their forms and changes, a pretty large object glass will be required, and the whole affair will become a matter of much greater nicety ; but for reading the daily history of the sun I should imagine a three-inch object glass would be ample. The representations should, if possible, be taken daily, and time carefully noted.'

It must not be supposed that this is a novel experiment. It has no claim to originality except as a continuous experiment. In 1842 Dr. Draper took a beautiful photographic impression of the solar spectrum in the south of Virginia, from which he deduced that negative rays exist on both ends of the spectrum, and do not depend on refrangibility. Whether he attempted at that time to take a portrait of the sun we are not certain,

but believe that he did so. It matters however but little who may have been the first to succeed in the bold design of taking the sun's photographic likeness ; it has now been done so often that by this time it must have been stereotyped, and many indications of the results to be anticipated from a consecutive course of observations have been already indicated. According to M. Wolf, the director of the observatory at Berne, the number of spots visible upon the disc of the sun return periodically, and the years in which the spots have been most numerous have been the driest and most fertile. In 1852 Professor Secchi, of Rome, took a daguerreotype view of the sun during an eclipse. This experiment seems to have been made, principally, for the purpose of testing the accuracy of M. Fizeau's statement that the chemical energy of solar light is more active in the rays which proceed from its centre than those which come from the edge of its disc. Having, as it would appear, confirmed this report, he extended his inquiries, and proved that the heat of the solar rays is twice as great at the centre as at the border of the sun's image, and that the maximum of heat is on the solar equator. If this be the fact, the equatorial regions of the sun are botter than the polar, and we must not only reject the old theory of the sun being a globe of fire, but calculate what effect the newly discovered condition of the sun would have on the climatology of the earth, not forgetting the supposition, already confidently expressed, that the two solar hemispheres have different temperatures, and con

sequently, that in estimating seasons, we must take into consideration which pole of the sun is turned to the earth.

The committee appointed by the British Association in 1852 to report on the physical character of the moon's surface, as compared with that of the earth, have a task which will probably occupy more time, if a thorough investigation be intended, than is expected. To collect and arrange the materials for the proposed report, if it is to be in any respect historical, will be a work of labour, but one of so much interest, that any man suited to the task must derive more pleasure from the investigation than from the anticipation of the credit to follow, although that will not be meagre if the execution be satisfactory. But in all probability this is no part of the design. The object is to obtain a series of photographic views of the moon, and to deduce from them, and from such observations as may be made, a theory of the physical constitution of that satellite. Dr. Robinson of Armagh made an attempt to take an image of the moon. For this purpose he took, as he supposed, a favourable opportunity, but failed; for after exposing a prepared surface for twenty minutes, no image was impressed. From this he deduced that lunar light has no chemical action upon the ioduret of silver ; but this generalization has not been supported by succeeding experiments. Sharp edged and well developed pictures of the moon have been since obtained by many astronomers, and there can be no doubt that other still more perfect pictures will be procured. We cannot now, from the want of time and space, even state, not to say investigate, the results obtained by Professor Ponzi, a geologist well acquainted with the volcanic districts of Italy, but the opinions of this observer will be carefully considered by Professor Phillips, who has in many particulars deduced the same conclusions from independent observation.

We must say one word about the progress of geology; that universally popular science which gains admirers everywhere, and students and co-operators from all classes --some to satisfy their curiosity, some their wonder, but others (and they are the larger number) to satisfy their love of inductive reasoning. To describe, and estimate the labours of the geologists during twelve months, would

occupy more pages than we are giving to all the reported doings of the British Association ; but there are always subjects of peculiar periodical interest, and these were last year the classification of the Silurian formations and the distribution of gold. Upon the former we have a few words to say.

Sir Roderick Murchison is fairly entitled to great honour for his investigation of the, so-called, Šilurian formations. The most enthusiastic of his admirers cannot, in this respect, award him a

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