Mädler's map. After alluding to the confusion likely to arise from the changes in the names he had before mentioned, Dr. Lee suggested that in future this plain be denominated “Otto Struve," as commemorative of the extensive labours of the astronomer of Pulkova; and he remarked in conclusion, that as Professor Chevallier and his daughter accompanied the expedition to Sweden to observe the total solar eclipse in 1851, and as Otto Struve and his daughter accompanied the Astronomer Royal and his daughter to Spain on the occasion of the total solar eclipse in 1860, so the young ladies of Bath would follow such good examples, and assist their fathers and brothers in their scientific pursuits.

Mr. Birt, in his paper On the Importance of adopting Methods for Detecting Changes in the Moon's Surface, commenced by alluding to the theories submitted for explaining the appearances on the moon's surface, one having reference to the fixity of those appearances, so that how long soever observations might be continued, no changes would be detected, all volcanic action on the surface—which appears to be admitted on all hands—having long ago ceased; the largest lunar forms having been the result of the most violent outbreaks, the medium forms indicating subdued action, and the smaller mountains, especially in the larger craters, resulting from the last expiring efforts. This theory, the author said, would not satisfy all minds, and, accordingly, astronomers were not wanting who leaned to the hypothesis that eruptive action still existed on the moon's surface, although in a subdued form. In order ultimately to set at rest the question as to whether the surface of the moon is in a state of quiescence or activity, Mr. Birt recommended the formation of a catalogue of lunar objects, remarking that our existing records were inadequate to determine the question. He gave instances of lunar craters, figured as far back as 1792, which were entirely omitted by Beer and Mädler (we have already referred to these in our pages); these craters the author had himself seen and recorded in his catalogue, in which 386 distinct objects are now entered.

THE HARTWELL OBSERVATORY.

(Continued from page 233.)

Speculum Hartwellianum; the Cycle of Celestial Objects continued at Hartwell Observatory to 1859. By Vice-Admiral W. H. SMYTH. 4to. London: Privately printed.

In our October number we gave a short account of the origin of this Observatory, with a description of the transit-room and the instruments therein. We have now much pleasure in resuming the subject, and proceed to give a few particulars concerning the instrument more immediately interesting to amateurs -the equatorial.

Three years after the completion of the transit-room, Dr. Lee commenced the building of his equatorial tower. Having procured an object-glass of nearly six inches diameter, he was anxious that it should be mounted with the completeness and efficiency of detail so successfully carried out with regard to the transit instrument; his arrangements, under the able superintendence of Admiral Smyth, and assisted by Mr. Charles May the Engineer, were at length perfected, and in 1850 the equatorial room was finished.

The object-glass alluded to, however, was not mounted in this room, as it was found, after being thoroughly tested, to be by no means a fine production, and, ultimately, the celebrated telescope used by Admiral Smyth in his observations for the Bedford Catalogue was erected, the Observatory at Bedford, after fulfilling its purpose, having been dismantled. This instrument is fully described in The Cycle of Celestial Objects, vol. i. pp. 337 et seq. The object-glass, of 5'9 inches clear aperture, and 8 feet 8 inches focal length, was obtained by Admiral Smyth from Sir James South, and was "deemed, perhaps, the finest specimen of the late Mr. Tulley's skill." It is mounted on the English plan, known as "Sisson's." The polar axis, 14 feet in length, is supported by stone piers, resting on brick foundations of a solidity equal to those constructed for the instruments in the transit-room, as mentioned in our former notice. On the head of the north pier, 10 feet above the floor, a cast-iron frame receives the upper pivot of the polar axis, the lower end of which carries the hour circle, reading both time and space, of 3 feet diameter, and connected with a very efficient driving-clock, regulated by governor-balls

similar to those of a steam-engine. The clock is remarkably steady in action, retaining a star on the wire of the micrometer very satisfactorily. The declination circle attached to the telescope is also 3 feet in diameter, and reads to 10" of arc.

The equatorial room is of circular form, the interior diameter being 15 feet, and the walls of the substantial thickness of 14 inches. It is surmounted by a hemispherical dome, constructed of wood upon a flattened ring of iron, a similar ring being firmly secured to the upper surface of the brickwork; and the dome rotates upon three iron spheres, each about 6 inches in diameter, interposed between the rings. The opening in the dome is equal to one-sixteenth of its circumference, having a shutter of copper somewhat less than an eighth of an inch thick, which turns upon a pin in the top of the dome, and is opened and closed by means of a handle and rackwork.

On the occasion of our agreeable visit to Dr. Lee in August last, we found the equatorial in full activity under Mr. Birt, who was employing the instrument to excellent purpose in obtaining measurements for his new and elaborate survey of the lunar surface.

The magnificent quarto, the title of which heads the present notice, gives a complete description of the Hartwell Observatory, and the purposes for which it was established. It is, moreover, a voluminous, very able, and highly interesting commentary or dissertation on astronomical discoveries, and other important subjects connected with the science, which have arisen and been made since the publication of The Cycle-1844; and, in particular, it contains a valuable series of further observations and remeasurements of a considerable number of double stars and other objects included in the Bedford Catalogue, with discussions thereon, the whole being brought down to the year 1859. The Speculum H. is also illustrated and enriched with many beautiful cuts and engravings.

The commencement of the year 1864 witnessed the production of a third and handsome volume, also from the prolific pen of Admiral Smyth, entitled Addenda to the Edes Hartwellianæ, wherein is collected a vast amount of information, both local and general-archæological, geological, numismatological, and (though last, to us not least) astronomical-forming, indeed, a most worthy companion to the two preceding works. The Admiral resides at

St. John's Lodge, a short distance only from Hartwell House; and on our brief visit to him during our sojourn at Hartwell, we found him still busily at work in the cause of Astronomy, he being at that time engaged in the preparation of his Sidereal Chromatics. This elegant brochure has been since completed and privately published; and we shall take occasion in an early number to offer to our readers a few remarks thereon.

ROYAL ASTRONOMICAL SOCIETY.

Third Meeting, January 13, 1865.

Warren De la Rue, Esq. F.R.S., President, in the Chair.
Secretary, R. Hodgson, Esq.

Thirty-two presents were announced, and among them the President called attention to M. Guillemin's treatise, Le Ciel.*

were balloted for, and duly elected Fellows of the Society.

The name of a gentleman was removed from the list of Fellows of the Society for non-payment of subscriptions.

The following were the papers of the evening :Observations of Comets IV. and VI. 1864, made by Mr. Hartnup, with the Liverpool equatorial.

An Approximate Ephemeris of Encke's Comet, prepared by Mr. Farley, presented by Mr. Hind.-The ephemeris comprised positions of the comet from January 22 to March 1; and it was announced that copies were in preparation for those Fellows of the Society who took an interest in and were observers of these faint objects.

* We understand that an English translation of this work will shortly be issued by Mr. Bentley. It is to be edited by Mr. Lockyer, and as additions will be made to the original work, which, both with regard to text and illustrations, is of a very interesting character, it will be an acceptable book to all English astronomers.

The Secretary remarked that the comet would be farther off and much fainter than on previous apparitions; but Mr. Farley had gone through the labour of computing the perturbations and calculating the ephemeris, in the hope that some of the large telescopes might pick it up.

The President remarked that, although none but large telescopes were likely to be useful in observing Encke's comet on this occasion, still it was wonderful what could be done with instruments of good definition.

Mr. Stone, On a New Form of Eyepiece, for determining the relative Brightness of Stars.-This is an adaptation to the eyepiece of two tourmalines, one being fixed and the other revolving. This arrangement, by the well-known polarising properties of the tourmaline, causes the image of the star, after its light has passed through one plate, to disappear when the second or analysing tourmaline is rotated, and to reappear at the next 90°. The angle of the vanishing point in two positions of the tourmaline is then read off on a small circle, giving, by the mean, a value peculiar to the star under observation as its point of fading out, which can be compared with other stars treated in the same way. Mr. Stone observed that the instrument in his hand was very roughly constructed, it being an experiment only; but that, nevertheless, it gave comparatively accurate results; and although the vanishing point differed in experiments made by Mr. Carpenter and himself, yet that as the ratio of each person's measures were accordant, the different powers of sight did not affect the principle of the instrument, which could be used for stars down to the fourth magnitude. With this apparatus the absorbent action of the atmosphere on stars of different colours might be observed. In answer to a question, Mr. Stone stated the colour of the tourmaline employed was a brownish one; and the President said it was to be regretted that colourless tourmalines were not to be obtained.

Mr. Drach, Mr. Beck, and Captain Noble having been named as Auditors for the accounts of the Society for the general meeting, Mr. Huggins, at the request of the President, prefaced the next paper by an account of his latest enquiry on the nature of the nebula. He stated that the most recent point discovered was that the great nebula of Orion was of uniform constitution throughout. All parts of it gave a purely gaseous spectrum, varying only in intensity. The bright lines were three in number;