and labour of learning, and by so doing, we feel sure that he can have done no harm, and that he has really enlisted many valuable hands in the service of science. We shall be happy to hear that the success of this volume induces Mr. Proctor to give us more.

SALE OF A LARGE ACHROMATIC.-The great refractor, by Cooke and Sons, of York, which was shown at the International Exhibition of 1871, was sold by auction by Messrs. Stevens, of King Street, Covent Garden, on the 12th ultimo, for about 750l. The instrument, which had every modern appliance, and was one of the most complete ever turned out by these celebrated makers, was of 10 inches clear aperture, and was originally priced at 1,200l., but owing to the rise in wages and materials would now be charged much more. The purchaser was Mr. Henley, the telegraph engineer.

Errata. In list of subscribers for Seecomber read Seccombe; for Hubbeosty read Hubbersty.

JOHN BROWNING begs respectfully to inform scientific

gentlemen and the public generally, that he has taken the Premises, No. 63, Strand, opposite Bedford Street. These premises he will open as a West-End branch of his business on the 18th of March. In a Show-room on the ground floor there will be every convenience for testing, or seeing in action, Microscopes, Spectroscopes, Astronomical, Electrical, and other Philosophical Apparatus. There are light workshops on the premises. Communication has been established by electric telegraph with the Factory at 111, Minories. JOHN BROWNING, Optical and Physical Instrument Maker to the Royal Society, the Royal Observatories of Greenwich and Edinburgh, &c., &c., &c., 63, Strand, W.C.; 111, Minories, E.; and 6, Vine Street, E.C. Specialities, Spectroscopes, Astronomical Telescopes, Polariscopes, Microscopes, and Electrical Apparatus.

VANTED, APPIANI ASTRONOMIA, large folio.

W

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The Astronomical Register.

No. 117.

SEPTEMBER.

1872.

THE BRITISH ASSOCIATION AND LUNAR WORK.

"He that putteth his hand to the plough and looketh back !"-we know the rest. Twenty years ago the British Association for the Advancement of Science put its hand to a work of no small magnitude and of no little importance. Unostentatiously it sought to throw light upon bygone Selenological changes through the instrumentality of accurate drawings of portions of the moon's surface; and some delineations of Gassendi, Plato, and the Mare Crisium, were executed by members of the first Lunar Committee. After a repose of eight years a partial revival took place, and a report was presented embodying some observations of the Crater Plato, in the course of which several objects in and around Plato were particularly examined. Four years later the energies of the Association were directed to a much greater work: the compilation of a catalogue of lunar objects accompanied by critical and explanatory notes, and assisted by a grant from its funds. The few following years, 1865 to 1868, witnessed an extension of the work, by the projection of a map on the scale of 200 inches to the moon's diameter, and during the four years four sections or areas of 5° in latitude and longitude were produced. These areas included every object that could be detected with ordinary telescopes, or found on existing photograms. At the meeting of the Association in 1868, objections were made to the great extent of the work and to the necessary slowness of its progress, which it was considered rendered it unsuitable for receiving the assistance of the Association, and, in consequence, the Committee was not reappointed at that meeting. Two years later the Association took up another line of lunar research, viz., the discussion of observations of lunar objects suspected of change, which has been continued for two years. The first year's work has been confined to an examination of the observations of the spots on the floor of Plato, and the second year's work to a similar examination of the observations of the streaks and markings on the floor. We find that the VOL. X.

Committee for carrying on these discussions has not been reappointed, and thus for the fourth time the Association has withdrawn from lunar work.

Of what value is this work which has been taken up in so desultory a manner by the British Association? On reviewing its progress we find in the first instance certain drawings produced, those which were published being three views of the Mare Crisium, by Professor Piazzi Smyth, under the morning, mid-day, and evening illuminations. An interesting series of unpublished drawings of Plato and the Alps are in existence. The labours of the revived Committee, in 1860, were confined to a single report. Much more work appears to have been effected by the Committees of 1864 to 1868. Nearly 500 objects on the four areas included by 10° of south latitude and 10° of west longitude, have been critically examined, and their outlines laid down on the scale above-mentioned. The catalogues of these objects, we are informed in the Report of 1869, contain numerous selenographical and selenological notices, having reference to the sequence of events, such as the protrusion of mountains, the formation of valleys, the appearance of ancient regions containing the remnants of grey plains and mountain ranges, which degrading agencies have so modified as to occasion them to present a very different aspect to that which we find characterising formations of a much more recent period, but still remote in selenological time; in fact, the Committee appear to have treated the subject they had in hand much as geologists have treated geological phenomena. Although a lunar survey of this kind must necessarily be one of great labour, consuming a large amount of time, the fixing of the lunar features to a definite epoch is of such great value in selenographical researches, that it is a matter of regret that it has been discontinued, especially as the amount of the grant never exceeded 120l. annually. One important result has grown out of this work, viz., the possibility, if not the probability, of detecting the changes occurring on the moon's surface by which deep craters such as Linné, previously described as very deep," have disappeared as if they had been filled up, has led to a very close inspection of the Crater Plato, which has been the subject of the most unremitting attention for at least two years. The discussion of the observations of Plato is the last work of the Association connected with the moon; it has shown that small spots varying in intensity of brightness and visibility are numerous on the floor, and that the streaks and markings which appear to be intimately connected with the spots, are also variable in form and brightness. The most striking result, however, is the darkening of the floor as the sun attains his greatest altitude above the horizon of Plato. These are certainly results which are leading us on towards a clearer conception of the state of the surface, and must contribute to the formation of views of the operation of forces, modifying that surface, of a character much nearer the truth than those formerly held.

66

So far as we are able to learn, the Association has withdrawn from this important work on account of its magnitude. The mapping of the surface in the way proposed consuming so large an amount of time, that its completion cannot be expected within any reasonable period, and with regard to the work, not less important, of observing definite portions of the disc, it may be remarked that, in order to detect such changes as the last Committee in its two reports has indicated, it is a work of considerable labour, and much time must be consumed in making the necessary observations. Now, it may be worth while to enquire if reasons such as these ought to weigh in retarding a work that promises to be of great benefit to future Selenographers? In the first place, no great work can

be proceeded with except it be step by step; each portion must be made good before the next is attempted, and if the aphorism

be kept steadily in view, and the main object not allowed to sleep, progress must result. Had the Association continued its grant, even if reduced to £100 per annum, it is more than probable that, by this time, four more areas of the map would have been completed, and a larger number of objects catalogued, and, as regards observations, we have reason to believe that by pursuing a course similar to that adopted by the last lunar Committee, a large number might be obtained capable of yielding important results. If these views be correct, it appears that the proximate effect of the withdrawal of the Association from the work has tended to retard it. Nevertheless, so far as the grants have been judiciously applied, the Association has been true to its designation; it has advanced the science of Selenography. In the second place, because the Association has withdrawn, and the work has been proportionately retarded, are we to come to the conclusion that it will languish and die out? By no means,-languish it may, but if there be energetic and devoted Selenographers, and they are upon the increase, the study of lunar physics will assuredly not die out. Observers will not be content

with the works of Schröter, Gruithuisen, Lohrmann, Madler, Smidt, and Bulard, but will seek in some way to bring their own work before the public, to place their observations on record, and to secure an examination and discussion of them, that their labours may not be lost, but that posterity may reap the benefit, should they not meet with a favourable reception at the hands of living astronomers.

HISTORICAL ECLIPSES.

Mr. J. R. Hind, writing from Mr. Bishop's Observatory, Twickenham, furnishes us (The Times) with the following interesting sketch of the Eclipses recorded in History:

"It is well understood that the historical eclipses, especially those of the sun, have an important bearing upon our knowledge of the elements of the moon's motion, as affording the means of testing the accuracy of those elements when carried back to very remote times. I send you a brief account of some results I have deduced in a systematic examination of these eclipses, making only such a selection therefrom as may possibly possess interest for the general reader. I shall omit any reference to the purely astronomical conclusions to which I have been led, which would be out of place in your columns, and, indeed, would extend this communication beyond reasonable limits. It may, however, be desirable to state that I have employed the last value of the secular acceleration of the moon's mean motion given by Professor Hansen, of Gotha, the author of the latest lunar tables, and have combined other important elements as determined by him with the results of M. Leverrier's tables of the sun. From recent investigations, it appears by no means improbable that we may have to rely wholly upon the ancient eclipses in fixing the true a mount of acceleration in the motion of our satellite.