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Astronomical and Meteorological Phenomena.

THE ROYAL OBSERVATORY.

ON Saturday, June 6, 1857, the Annual Visitation of this great national establishment took place, on which occasion the AstronomerRoyal presented his Report to the Board of Visitors on the condition of the Observatory, and its history during the past year. This document contains, as usual, several interesting features in connexion with the progress of Astronomy.

The Instruments, with a few trifling exceptions, are in the same condition as they were last year. The new S.E. Equatorial, which promises to be one of the finest instruments ever made, is now nearly completed. Messrs. Merz, of Munich, have not, however, yet succeeded in making an object-glass to their satisfaction.

The Meridional system of Astronomical Observations, for which the Greenwich Observatory is so deservedly celebrated, is rigidly preserved. Each star of a large clock-star catalogue is observed, if possible, twenty times in three years; some stars are observed for refraction; some as having been compared with the Moon; some on suspicion of proper motion, &c. The Moon is observed at every opportunity without exception. The Sun and Planets are observed at every opportunity, except on Sundays, and when they pass later than 15 in the morning, in which state the large planets only are observed, and only when the moon also is to be observed. The transits have been observed almost entirely by the chronographic method, except for the close circumpolar stars.

The whole number of Meridional Observations from 1856, May 19, to 1857, May 23, is as follows:-In the Department of Transits Observations of Transits (reckoning two limbs, or two methods of observation by ear and by touch, as two observations), 4169; Observations of Collimator, by the Telescope of the TransitCircle, 311 pairs; Observations of Transit-wires by Reflexion, 310; Observations of one Collimator by the other, 52. In the Department of Zenith Distances (reckoning two limbs, or a combination of Direct Observation with Reflexion Observation, as two observations, and including the observations of the wire by Reflexion), Circle Observations of all kinds, 3663.

A curious fact has been noticed with respect the Azimuth of the Transit-Circle and the Azimuth of its Collimator. Mr. Airy observes:- "There is a well-marked annual periodical change in the position of the Transit-Circle, the southerly movement of the eastern pivot having its minimum value in September, and its maximum in March, the extreme range being about 14 seconds; and there is a similar change, but of smaller amount, in the position of the Collimator. I cannot conjecture any cause for these changes, except in the motion of the ground. There is a very frequent change of still smaller amount in the Azimuth of the Transit-Circle, accompanied

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by a nearly equal change in the apparent Azimuth of the Collimator, so that from day to day the Transit-Circle and Collimator preserve their relative position unaltered; these I conceive to be the effects of accident in observation of the circumpolar stars, arising either from fault of the observer, or from irregularities either in the level or in the collimation; at the same time, viewing the great accuracy of the observations of circumpolar stars, and the extreme simplicity of the pivot-supports and of the instrument-frame, I cannot conjecture how such irregularities can arise."

During the past winter Mr. Airy received intimation from Professor Hansteen that the dip, as determined at Greenwich, appeared to have become greater than was consistent with the changes of dip going on in the north of Europe. A similar discordance was found to exist between Greenwich and Kew. This led Mr. Airy to examine the Royal Observatory instrument, and it was found so imperfect in its mechanical construction, that when the needle was lifted up from its agate bearings its upper point almost always struck the brass circle. These defects have been amended, and the apparent dip is diminished by nearly the quantity which Professor Hansteen conjectured. Mr. Airy regrets that this irregularity unfortunately causes the dip-observations at Greenwich for several years past to possess very little value.

The Magnetical and Meteorological Observations continue to be made on the system of self-registration, commencing with August 25, 1856; the thermometers in the magnet-boxes have been read at twenty-four consecutive hours once in every week, with the view of obtaining bases for complete reduction of the observations. Mr. Airy contemplates, as soon as he shall have some computers liberated from the lunar reductions, to take in hand the further reduction of the magnetic observations.

Under the head of Chronometers, Communications of Time, and Operations for Longitude, Mr. Airy makes the following observa

tions:

"The number of chronometers in the chronometer-room is sixtyeight. All are compared with the Mean Solar Clock, which is sympathetic with the Corrected Motor Clock of the Galvanic System: some every day, others once in the week. The chronometers on trial for purchase have, for several years past, been sometimes exposed to extreme temperatures; and lately I have determined to extend this system in a lower degree to the Admiralty chronometers, subjecting all in turns to artificial heat as high as 80° Fahrenheit. The Observatory takes charge of the valuation of chronometers to be purchased by the Government, and of the receipts, repairs, and issues of chronometers belonging to the Government. The Motor Clock of the galvanic sympathetic system is adjusted every day, after comparison, by means of an auxiliary pendulum, which is put in mechanical connexion for a time with the clock pendulum, and by which the rate of the clock is either accelerated or retarded by of its whole value as long as the two pendulums are united. By this clock our own sympathetic connexion is maintained, and time

signals are sent to other places. I am desirous of introducing the system of galvanic connexion for clocks of small dimensions; a system which would frequently be very convenient. The number of failures of the Time Signal Ball at Deal, dropped by galvanic current from the Royal Observatory, in the course of one year has been nineteen. When it is considered that four connexions must be made on the line before it is fit to receive our current, and that then there must be four contacts at Greenwich and one at Deal, this number of failures will appear very small. Other time signal balls are dropped by currents issued at the same time, at the Strand, Cornhill, and Liverpool; but though I am happy to supply with regularity the currents required for these purposes, I do not hold myself responsible for their success. I have verified experimentally the perfect practicability of dropping a ball at Devonport by a current from Greenwich."

The value of these galvanic clock communications is very great; the clock in the Lombard-street Post-office is adjusted and regulated by the apparatus with the greatest regularity. Besides this, sympathetic movements are maintained with other clocks, and hourly signals sent through the wires of various railways by which time balls are dropped at the Strand, Cornhill, Liverpool, and Deal. The communication with the Post-office clock is remarkable. At 23h. 26m. Os. of that clock a signal is given to Greenwich, the comparison of which with the Royal Observatory's clock acquaints the Observatory with the error of the Post-office clock. At 0h. 0m. Os. of the Greenwich clock a signal is sent from Greenwich, which mechanically adjusts the Post-office clock. At 0h. 26m. Os. of the Postoffice clock a second signal is given to Greenwich, by which the efficiency of the adjustment is shown. The system answers so well that it is purposed to extend this system to other clocks.

The Astronomer-Royal concludes his Report by expressing his entire satisfaction with the zeal of the assistants and observers placed under him. The duties of the Observatory have been so well performed that the ordinary astronomical reductions are now more completely brought up to a level with the observations than at any period within Mr. Airy's recollection. At the same time the Astronomer-Royal wishes to see improvements in the education of his assistants, which would at once be creditable to the establishment which he directs, and beneficial to science.-Athenæum, No. 1546.

SPOTS ON THE SUN.

THE Astronomical Society have presented their Medal to M. Heinrich Schwabe, of Dessau, who has made daily observations of this phenomenon for a period of thirty years; and the President's address on the occasion of presenting the medal offers in itself an interesting reply to the queries of our astronomical correspondents. The result of M. Schwabe's investigations has been to establish, with a degree of probability almost amounting to certainty, that the Solar Spots pass through the phases of maximum and minimum frequency, and vice versa, through a period not very different from

ten years; but that during the last three years the results have shown symptoms of disturbance.

M. Schwabe's merits are in no way affected, though, no doubt, the value of his discovery is enhanced by this remarkable episode. No longer is its scope confined to the disclosure of a physical peculiarity in the constitution of the Sun. It promises to be the means of revealing the prevalence of a principle, throughout the solar system, co-extensive with gravitation, and of establishing another link in the chain of analogies binding earth with other worlds, the ultimate effect of which on the progress of physical research no one can foresee.

THE AUGUST METEORS.

M. COULVIER GRAVIER, the zealous observer of these Meteors, gives the following Report for the month, from 13th July to 13th August, in the past year. The figures show the mean hourly number of falling stars at midnight :

In

It will be seen that there is a pretty regular increase from the 22nd July to the 10th August, where the maximum occurs as usual. another table, he gives the mean hourly fall for twelve years (1846-1857), from 20th June to 31st August, by averages for each three days. From this second table it appears that the number of meteors is pretty uniform from 20th June to 20th July, varying from 5 to 9; from 23rd July it increases pretty regularly to 7th August, when it reaches 27.8; at the 10th August it leaps up to 69.9; on the 13th it is 312, and then falls gradually to 10.7 on the 31st. The present maximum is thus beneath the average, and M. Gravier concludes, as he did last year, that the number of the Sir John Herschel August meteors is gradually diminishing. observes that the August meteors, though less brilliant than those of November, are more certain, as the latter sometimes disappear for some years. M. Leverrier announced lately that the observations made under his direction on a former occasion to discover the height of the meteors, would be repeated this year, and that the stations chosen for observers were Paris, Melun, and Rambouillet, forming a nearly equilateral triangle with a side of 48 kilometres (30 miles). If a fire-ball, or remarkable falling star, capable of being distinguished from the others, is observed from these three stations, and its angle with the horizon at each taken, its height can be found by calculation.-Scotsman.

Mr. T. Forster, the well-known astronomical observer, at Ostend, witnessed the Meteors on August 12 as of very unusual forms and colours. From a good position above the sea he watched them great part of the night. Many hundreds fell in various directions, but particularly towards S. W. and W., not N. W. as usual. They did not

in general move fast, and leave the white trains behind them, as is usual, but descended slowly with a bright yellow flame; others were splendidly crimson, and some bright-blue and purple. This fact is very curious, as favouring the hypothesis of ignited gases adopted by M. De Luc of Geneva. During the whole of August, meteors were numerous all along the Rhine and in Germany. Such numbers had not fallen since the 10th August, 1811, nor have we any record of such a quantity as on the present occasion, extending over four days consecutively, and exhibiting such very brilliant and diversified tints of light. Collaterally with these meteors the following phenomena should be noticed, proving the highly electric state of the air. In the storm which raged in Holland on the 5th July, the hailstones were larger than pigeons' eggs, and broke nearly all the windows in Arnheim. The same occurred at Spa on the 5th of August, when every pane of glass exposed to the hail was beaten to pieces. All the electrical instruments indicated a high positive charge. A trombe or waterspout was witnessed by Mr. Forster in the distance on the 11th.

TWINKLING OF THE STARS.

A CORRESPONDENT (M. F.) in the Philosophical Magazine, No. 86, writes:-"The stars twinkled much at Brighton on the evening of the 16th of March. Sirius and Aldebaran were in sight; and on passing the axis of the eyes across them so as to produce a changing place for their image on the retina, it was seen that the difference due to twinkling was so great as at certain moments to cause the apparent extinction of the stars. A mirror was therefore held in the hands so as to send a reflected image of the selected star to the eye, and then the mirror was moved in such a manner as to throw the image of the star in a line or circle, which could easily be done. Upon examining the brightness of the star image at the moment when it was reflected from different parts of the moving mirror, the light was seen to differ enormously, and very frequently, indeed, to be replaced entirely by darkness. In fact, the successive phases of the star, which, being seen in one direction, gave a continual but wavering light, were now separated into their luminous and their absolutely dark conditions; and thus the effect of twinklings was made far more manifest than by the ordinary mode of observation. The apparent extinctions were not for long together; but they often cut up a circular path of light of about 10 degrees angular space into six, seven, or eight parts, separated by short dark intervals without sensible light.

STARS ON THE DISK OF THE MOON.

MR. HIPPISLEY, of Stow Easton, near Bath, has related to the Astronomical Society an experiment which he lately performed for his own satisfaction, illustrative of the projection of Stars on the Disk of the Moon. He formed an artificial star with a candle placed at a distance of about 185 yards, and an artificial moon with a disk of card attached to a rod applied to the end of his telescope. Illuminating his artificial moon, he was able to make the relative brightnesses of the artificial moon and star nearly in the proportion