On some of the Characteristic Differences between the Configuration of the Surfaces of the Earth and Moon. By Professor HENNESSY, F.R.S. The author pointed out that the peculiarities observed on the surface of our satellite should be ascribed to the sole action of volcanic forces, whereas those which we find on the earth result from a combination of volcanic and atmospherical agencies. In order more perfectly to study these contrasts, he called attention to the most characteristic feature of all lunar volcanos, namely the ring- or hoop-shaped crater, surrounded by circular, nearly concentric ridges. On the earth's surface, volcanos deviated more or less from this type; and if the deviations are due to the differences between terrestrial and lunar superficial forces, it must follow that such differences will be most distinctly manifested in those cases where such terrestrial forces possess the highest degree of energy. He illustrated this proposition by referring to the peculiar structure of the volcanos in the island of Java, where the action of tropical rains and hurricanes has been effective in producing the widest differences between the terrestrial volcanic summits and those observed on the moon's surface. While the hooped structure of the latter cannot be traced among the views of Javanese volcanos which are presented in the comprehensive work published by Dr. Junghuhn, we frequently find diagrams of volcanic cones showing radiating ribs like those of a folded lamp-shade or an umbrella half closed, an appearance due to the very regular manner in which the tropical torrents scoop out the friable and scoriaceous summits of the craters. The contrast which arises by comparing some of these drawings with the best lunar diagrams and photographs may prove highly interesting to geologists as well as to selenographers. On a Brilliant Elliptic Ring in the Planetary Nebula, AR 20° 56′, N.P.D. 101° 56′. By WILLIAM LASSELL, F.R.S.; in a Letter to Dr. Lee, F.R.S. 9 Piazza Sliema, Malta, 26th Sept. 1862. MY DEAR SIR,-In directing my large equatorial upon the well-known planetary nebula situated in RR 20h 56m, N.P.D. 101° 56' (1862), it has revealed so marvellous a conformation that I cannot forbear to send you a drawing of it, with some description of its appearance. With comparatively low powers, e. g. 231 and 285, it appears at first sight as a vividly light-blue elliptic nebula, with a slight prolongation of the nebula, or a very faint star at or near the ends of the transverse axis. In this aspect the nebula resembles in form the planet Saturn when the ring is seen nearly edgewise. Attentively viewing it with higher powers, magnifying respectively 760, 1060 and 1480 times, and under the most favourable circumstances which have presented themselves, I have discovered within the nebula a brilliant elliptic ring, extremely well defined, and apparently having no connexion with the surrounding nebula; which indeed has the appearance of a gaseous or gauze-like envelope, scarcely interfering with the sharpness of the ring, and only diminishing somewhat its brightness. This nebulous envelope extends a little further from the ends of the conjugate than from the ends of the transverse axis; indeed it is but very faintly prolonged, and only just traceable towards the preceding and following stars. There is a star near its border northwards, in the projection of the conjugate axis. The breadth or thickness of the ring is, unlike that of Saturn, nearly uniform or equal in every part, so that its form most probably is either really elliptic, and seen by us in a line nearly perpendicular to its plane; or if really circular and seen foreshortened, a section through any part of it limited by the internal and external diameters must be a circle. In other words, it will be like a circular cylinder bent round. It could scarcely fail to bring to my mind the annular nebula in Lyra, especially as there is a conspicuous central star (proportionally, however, much brighter than that which is in the centre of that nebula); and yet the resemblance is only rudely in form; for this ring is much more symmetrical and more sharply defined, suggesting the idea of a solid galaxy of brilliant stars. The ring is not perfectly uniform in brightness, the south-preceding part being slightly the most vivid. The transverse axis is inclined to the parallel of declination about 13°. A series of micrometrical measures of the length and breadth of the ellipse, gives a mean of 26"-2 for the transverse, and 16′′-6 for the conjugate axis. The accompanying drawing has not been at all corrected by these measures, but is the result of several sketches made during different observations, and is a faithful transcript of the appearance of the nebula to my eye, when most favourably seen. The object is, as may be supposed, one of extreme difficulty, requiring in the highest degree the combination of light and definition in the telescope, and a favourable state of atmosphere,-which will further appear when I state that it was not until I was favoured with an unusually fine night, and had applied a power of 1480, that the whole of the details were brought out. I confess I have been greatly impressed by the revelation of this most wonderful object, situated on what perhaps we may consider as the very confines of the accessible or recognizable part of the universe, affording ground for the inference that more gorgeous systems exist beyond our view than any we have become acquainted with. I am, &c., W. LASSELL. Observed R.A. and N.P.D. of Comet II. 1862. By the Rev. R. MAIN, M.A., F.R.S. This paper gave the results of observations of the comet from August 5 to August 29, on ten nights. It was observed on the meridian with the Carrington transitcircle on August 7 and 9, and off the meridian with the heliometer, used as an ordinary equatorial, on August 5, 7, 9, 14, 18, 19, 22, 23, 25, and 29. The observations have been rigorously reduced, and all necessary corrections for refraction, parallax, &c. have been applied. The assumed mean places of the companion stars for 1862, January 1, taken mainly from the Radcliffe Catalogue of Circumpolar Stars,' were also given. On the Dimensions and Ellipticity of Mars. By the Rev. R. MAIN, M.A., F.R.S. This paper gave the results of seven sets of measures of the disk of Mars, made for the determination of his ellipticity with the heliometer, by the method of contact of limbs of the two images formed by the half-object-glasses. The power used was 300, which is found by experience to be very suitable for such measures. The direction of the polar diameter was determined by a well-defined circular white cap near the southern limb, the centre of which was assumed to be coincident with the South Pole. The directions, separately estimated, of the polar and equatorial diameters agreed well on separate evenings, their difference never deviating much from 90°, thus proving the precision of the estimations. The measured diameters have been corrected for defect of illumination. The following are the results of the measures: Mr. Main drew particular attention to the difference in the degrees of consistency in the results for the polar and for the equatorial diameter, the latter agreeing sur prisingly well from night to night, while the former exhibit discordances of considerable amount. This it is difficult to account for, except on the supposition that the snowy cap before referred to may have had some influence in distracting the eye from the real borders of the images in making the contacts. Still, on the whole, the measures all agree in establishing a measurable ellipticity, and Mr. Main intended to continue them at every opportunity during the present opposition, with the utmost care and caution. On some Peculiar Features in the Structure of the Sun's Surface. By J. NASMYTH. The author gave a short sketch of the character of the sun's surface as at present known. He described the spots as gaps or holes, more or less extensive, in the luminous surface or photosphere of the sun. These exposed the totally dark nucleus of the sun; over this appears the mist surface-a thin, gauze-like veil spread over it. Then came the penumbral stratum, and, over all, the luminous stratum, which he had discovered was composed of a multitude of very elongated, lenticular-shaped, or, to use a familiar illustration, willow-leaf-shaped masses, crowded over the photosphere, and crossing one another in every possible direction. The author had prepared and exhibited a diagram, pasting such elongated slips of white paper over a sheet of black card, crossing one another in every possible direction in such multitudes as to hide the dark nucleus everywhere, except at the spots. These elongated lens-shaped objects he found to be in constant motion relatively to one another; they sometimes approached, sometimes receded; and sometimes they assumed a new angular position, by one end either maintaining a fixed distance or approaching its neighbour, while at the other end they retired from each other. These objects, some of which were as large in superficial area as all Europe, and some even as the surface of the whole earth, were found to shoot in thin streams across the spots, bridging them over in well-defined streams or comparative lines, as exhibited on the diagram; sometimes by crowding in on the edges of the spot they closed it in, and frequently, at length, thus obliterated it. These objects were of various dimensions, but in length they generally were from 90 to 100 times as long as their breadth at the middle or widest part. Observations on Three of the Minor Planets in 1860. The first observation of Eunomia was made with the parallel wire micrometer, and power 110; all others with the ring micrometer, and power 84 of the Hartwell Equatorial. The comparison stars employed were as in the annexed list : The following magnitudes have been carefully estimated; generally, by comparison with apparently similar objects in the nearest variable star-map then in course of construction: Victoria, 1860, April 3...... 10-5 mag. | Eunomia, Sept. 1, 8-2; Sept. 4, 8'6; Sept. 7, 8.3. 9...... 10.5 Sept. 1...... 9.0 Metis The preceding observations of minor planets were the last made by Mr. Pogson before leaving England for Madras in January 1861; it was his intention to reduce them speedily, and to send them to me from Malta or Alexandria; but, as anticipated, the inconveniences of a sea-voyage prevented him from fulfilling his design, and the pressure of official duties in his new position has not permitted him to attend to his former unfinished pursuits until recently. On the Excentricity of the Earth, and the Method of finding the Coordinates of its Centre of Gravity. By W. OGILBY, F.G.S. On the probable Origin of the Heliocentric Theory. By J. SCHVARCZ. The author traced the origin of the Copernican system to Pythagoras, through Aristarchus the Samian and Archimedes of Syracuse. On Autographs of the Sun. By the Rev. Professor SELWYN. The author showed several "autographs of the sun," taken with his "heliautograph" by Mr. Titterton, photographer, Ely, which consists of a camera and instantaneous slide by Dallmeyer, attached to a refractor of 24 inches aperture by Dollond; the principle being the same as that of the instrument made, at the suggestion of Sir J. Herschel, for the Kew Observatory. The autographs are of July 25, 26, 28, 29, 31; August 1, 2, and August 4, 10.15 A.M. and 11.30 A.M. (a series of bright days coincident with a large group of spots); August 19, 20, 23 and 25, where the same group reappears, much diminished; September 19, 23, 26, 30, Oct. 1, in which is seen a group of 118,000 miles in length. On the 23rd three autographs were taken, two of them with the edge of the sun in the centre of the photographic plate, showing that the diminution of light towards the edges of the disk is a real phenomenon, and not wholly due to the camera. In the two of the 4th of August, where the great spot (20,000 miles in diameter) appears on the edge, a very distinct notch is seen, and the sun appears to give strong evidence that the spots are cavities; but eye observations and measurements by the Rev. F. Howlett, and others, tend to show that this evidence is not conclusive, for there was still a remaining portion of photosphere between the spot and the edge. The phenomena shown in these autographs appear to confirm the views of Sir J. Herschel, that the two parallel regions of the sun where the spots appear, are like the tro2 1862. pical regions of the earth where tornadoes and cyclones occur, and those of Wilson in the last century. The facule are clearly shown, and seem to prove that the tropical regions of the sun are highly agitated, and that immense waves of luminous matter are thrown up, between which appear the dark cavities of the spots, whose sloping sides form the penumbræ, as explained by Wilson and others. Other analogies between solar spots and earthly storms were pointed out, and reference was made to the glimpses of the structure of the sun exhibited by Mr. Nasmyth as confirming the above views. On the Hindu Method of Calculating Eclipses. By W. SPOTTISWOODE, F.R.S. The astronomy of the Hindus is contained in a series of works known by the general name of "Siddhanta." These have been composed at different times over a period of 2000 years. In them are some incidental allusions to the configurations of the heavenly bodies, by means of which Baily, Davis, and others have attempted to calculate the dates of some of the works. There were two points to which the author drew particular attention, viz. the process of correction whereby the true longitudes were deduced from the mean, and the precession of the equinoxes. It had been noticed that the apsides, or points of slowest movement, and the positions of conjunction with the sun had proper motions. These were attributed to influences residing in the apsides and conjunctions respectively, and corrections due to each were accordingly devised. The undisturbed orbit was considered a circle, with the earth (E) in the centre, and upon it the centre of a smaller circle or epicycle moved with a uniform angular velocity equal, but opposite in direction, to that of the undisturbed planet; so that M being the centre, and m any given point on the epicycle, Mm always remained parallel to itself. If, then, at the apse or conjunction (according as the correction of one or the other was being calculated) Mm was in a straight line with EM, the true position of the planet was conceived to be at the point where Em cut the undisturbed orbit. The radius, moreover, of the epicycle was variable, and its magnitudes at the odd and even quadrants being determined so as to satisfy observation, its intermediate variation was considered proportional to the sine of the mean anomaly. The precession of the equinoxes is an important elemen in Hindû astronomy, not only as a question of scientific accuracy, but also as marking an epoch in the history of discovery. It is an ascertained fact that their earlier writers, among the foremost of whom Brahmagupta may be mentioned, took no account of it whatever. The statement in the Surya Siddhanta, when divested of its obscure terminology, seems to amount to this, that the sidereal circle shifts on the zodiac with an oscillating motion, whose period is 7200 years, and whose maximum range is 27°. This gives an annual rate of 54". On some Improved Celestial Planispheres. By C. J. VILLA. LIGHT AND HEAT. On the Means of following the Small Divisions of the Scale regulating the Distances and Enlargement in the Solar Camera. By A. CLAUDET, F.R.S. The author, in a former paper, had proposed a new method for measuring both the distances of the negative and screen for any degree of enlargement of the image, by means of a scale or unity divided into 100 parts, and smaller fractions if possible. This scale being fixed on the table of the optical apparatus, an index connected with the frame holding the negative was brought exactly on any division of the scale which was indicating the proportion and distance of the image. This arrangement would be very complete and satisfactory if the scale were always long enough to be marked with divisions sufficiently conspicuous; but the shorter the focus of the object-glass, the smaller the divisions of the scale must be. In order to meet this difficulty, he has adopted the following plan:-He traces on the table an equilateral |