147 TRANSIT OF VENUS. We are very glad to be able to announce that the United States Senate has unanimously passed a bill, appropriating 50,000 dols. to meet the expenses of the observations upon the transit of Venus in 1874, on the part of the National Observatory in Washington. The bill has been introduced into the lower house, and will doubtless soon become a law. Nature. NOTICE OF A LECTURE BY PROFESSOR G. B. DONATI, ON "AURORA BOREALES, AND THEIR COSMICAL ORIGIN."* Only the very few Italians who had travelled to regions much nearer the poles than their own country, had seen a grand aurora before October, 24, 1870. * Description of aurora of February 4, 1872 * About 8 p.m., there appeared in the south, in the constellation of Orion, luminous waves of no great size, which becoming continually brighter, mingled together; broke, disappeared, and re-appeared in forms always different; and finally arranged themselves like thin and very white darts, which formed a small but most beautiful crown, in fashion like a fan, with its concavity turned below. It seemed as if they formed an aurora australis on a smaller scale than the great general aurora. Theories of Halley, Coates, and Marian. Electric theory insufficient. Electrometers do not indicate an extraordinary increase of electricity in the atmosphere during the development of auroras. Explanation of the auroral phases as a magnetic phenomena. That the aurora is an electromagnetic phenomenon no one can now doubt-but are electricity and magnetism its cause, or merely its effect? The researches of Loomis prove that the number of auroras has a maximum and minimum about every ten years and this is also confirmed by the examination which I have begun of a long series of records relative to auroras, in the observatory here * * * By that series it appears that in the period of about ten years, there are two or three consecutive years during which fine auroras are seen in places which are not very near to either of the poles of the earth ; whilst in the intermediate years they are either not seen in those same places, or if seen are only very faint.† Since no known atmospheric phenomena can account for this decennial period, it is necessary to examine whether auroras, in place of being classed with purely meteorological, are not rather to be regarded as cosmical phenomena. This was Marian's supposition in 1733, and Olmsted's in 1856. Differing, however, from the special theory of the latter, Professor Donati proceeds to inquire whether auroras are really situated mainly in our atmosphere. From the most accurate and recent observations, the principal phenomena of auroras happen at distances from the earth varying from 100 to 260 kilometres (from about 60 to 160 miles) and no physicist has assigned a greater height to the atmosphere than 60 kilometres (about 40 miles). It is impossible to deny that the auroral phenomena happens *Extracted from the "Nuova Antologia," March, 1872. + The years of the present century in which fine auroras were seen in almost all Italy, though less striking than those recently observed, were 1805, 1826-27, 1837-3839, 1848, 1859-60, 1870-72. It is seen at once that to obtain the decennial period above indicated there is wanting only the year 1815; nevertheless, in 1814 an aurora was seen at Parma. (for the most part at least) far beyond the limits of the atmosphere, which is also the case with not a few of the falling stars which become visible to us far beyond those same limits. But it is unquestionable that neither of these phenomena can occur in a void. What then exists there? Poisson imagined an electric atmosphere above our own. Quetelet supposes another atmosphere which he call etherial; material indeed, but with a nature and composition quite different from ours. Donati thinks this very probable; only instead of electric or etherial, he would prefer to call it cosmical, or, better still, solar, if this last would not lead to confusion, since it cannot but be a portion of that which, before the origin of our planetary system, must have surrounded, and which still surrounds our sun, from whose mass and atmosphere, according to the most generally accepted cosmogonical ideas, all the planets, including the earth, must have come forth. He next refers to the ten years (about) corresponding maximum and minimum of the solar spots, of the deviations of the magnetic needle, and of the frequency and splendour of the auroras. the maxima, however, are not equal. In the number of the solar spots, about every sixty years there is a maximum greater than the intermediate maxima; and such a period of maxima amongst maxima appears also to have been sufficiently established with regard to the magnetic needle and the auroras. What is the correspondency or isochronism in these cosmical phenomena ? All Kepler* supposed, and many since have also tried to prove, that the ruling force in our solar system is no other than a result or transformation of magnetism. That the forces of nature are mutually and alternately transformed in a periodical and endless cycle, and that from such transformation arises all the life of the universe, is sufficiently proved by many facts; and therefore nothing is opposed to the admission that universal attraction and magnetism may be forces of which one is a consequence of the other, and which are nearly identical. But even without such conceptions, why may not magnetism act at the same immense distances as gravitation; and who shall deny that the sun and planets are as much magnetic bodies as the earth, and in most cases even more powerful? The only difference to be kept in mind is that whilst gravitation varies with the distances of the bodies, magnetism varies according to their relative position. If then it be admitted, as seems natural, that there is a continuous interchange of magnetic currents amongst the various bodies of our system; if, that is, there exists a cosmical magnetism, this may afterwards combine with the proper and peculiar magnetism of every individual body, and determine in it phenomena that are special and inherent in its particular nature. Thus, for instance, it may determine on the sun the production of spots, and many other phenomena continually observed: on the earth it may be the cause of auroras, and the variations of the needle: and in the other planets of other different phenomena, of which this is not the place to speak. But these currents at certain periods will be stronger or weaker, according to the position occupied by the planets in regard to themselves and to the sun; consequently, the derived phenomena also will be subject to consimilar periods.† *Astronomia Nova. + Donati in a note refers to his lecture on this subject in January, 1869, and says that since 1871, Professors Serpieri and Tacchini have continued their observations, which confirm the opinion he expressed in 1869. [See also a paper on Further investigations on Planetary influence upon Solar activity, by MM. De la Rue, Steward, and Loewy, in Nature, March 28, 1872]. (To be continued.) 149 REVIEWS. Conversations on Natural Philosophy. By Mrs. Marcet. We hail with pleasure the fourteenth edition of this useful and entertaining work, which has been revised and edited by the author's son, Francis Marcet, F.R.S. It has been made more complete by the introduction of two additional conversations on Spectrum Analysis and Solar Chemistry. The former principally derived from Mr. H. Roscoe's book upon Spectrum Analysis. It is astonishing in how clear and entertaining a light most of the leading facts of Natural Philosophy are explained in these dialogues. The whole is made plainer still by the numerous plates with which the volume is furnished. Pamphlet of Extracts from the Thirteenth Volume of Astronomical Observations made at the Royal Observatory, Edinburgh. By C. Piazzi Smyth. The title of this work gives a faint idea of its size and importance, it being a handsome 4to vol., of about an inch thick. It contains star catalogues from observation, a reprint of the immensely laborious account of observations of the Great Pyramid, which we noticed some time back. The form is much improved, especially as regards reference to the plates, to which there are some additions. A paper on Auroral and other faint Spectra; another on Scottish Meteorology, from 1856 to 1871; one on the Hyperborean Storm of Oct. 2nd and 3rd, 1860; and, lastly, a general description of the Royal Observatory, Edinburgh, and its occupation. There is an enormous amount of interesting matter in the volume. The paper upon faint spectra, in which some usually accepted dicta are questioned, is worthy of being well considered. NEW NEBULE. M. Borelly, of Marseilles, has communicated to the Astronomische Nachrichten the following catalogue of new nebulæ discovered by him at Marseilles. The positions are for 1872. S. Polar Distances. R. A. h. m. 6 39 21 5 26 3 6 48 44 8 51 44 II 72 28 20 II 45 72 25 46 3 25 18 72 43 31 Nébuleuse assez faible, étendue, de forme elliptique, pas de point brillant. Nébuleuse excessivement faible, à peu près ronde, presqu' inobservable. NEW VARIABLE STAR. M. Borelly notes a new variable star in R.A. oh. 17m. 17s., and Decl. S. 10° 10' 10". On November 3, 1871, its magnitude was 63; on November 8 it had sunk to the 8th magnitude, and on November 24 to the 10th magnitude. From November, 1871, to January, 1872, it underwent no change; and since then it has been invisible. LUNAR OBJECTS SUITABLE FOR OBSERVATION IN JUNE, 1872. BY W. R. BIRT, F.R.A.S., F.M.S. The lists for March and May, 1871, are available for observation in June, 1872. On p. 105 of the April number of the present volume, we have given supplement < o from the 23rd, is the 31st of March, 1871, viz., 147° 34' diminishing to 59° 4′. In Vol. IX., p. 128, the value of supplement < on May 21, 1871, was 152° 21', and on May 31, 1871, - is was 32° 8'. In the month of June, 1872, the value of supplement < on the 8th at midnight is 148° 37' diminishing to 31° 35′ at midnight of the 18th. The two lists can therefore be combined as recommended for April and May. It is necessary to remark that on the 26th of May, 1871, neither Piazzi Smyth nor Rumker were in sunlight. These craters may be looked for on the evening of June 13, and, if not then, in sunlight on the following evening, June 14. There is an erratum in note (k), for Gandibert read Gaudibert. Sixth Zone of objects from North to South. Atlas, Oersted, Franklin, Berzelius, Prom: Archideum (a), Tralles, Mare Crisium the eastern part, Picard with A and B of B and M, Snellius, Stevinus, Biela. (a.) Prom. Archideum, a mountain range with a steep promontory to the North, between Geminus and Berzelius. It has a crater a of B and M opened on its northern summit. This zone contains the interesting objects on the eastern part of the Mare Crisium, which have been very carefully studied by Webb. The six zones lately given will afford ample employment for the telescope, as the morning and evening terminators recede from the western limb, the objects can be well studied under the sunset illumination during the autumnal months. On June 18, or earlier if in sunlight, the cleft from Hesiodus to Capuanus will form a fine study. Mr. Knobel has succeeded in tracing the cleft throughout its length without interruption. Observations of the cleft with large instruments are desirable. LINNE. The cone of Linné was observed as a small object on April 14. My record is as follows, "1872, April 14, 8.50 to 9.25 G.M.T., aperture 2.75 inches, power 100. IE y3, IE 0' and I E 02 very distinct; also the ridge I E y24, and the ridge forming the west boundary of the depression in which Linné is situated. At 8 hours this ridge was exactly on the terminator, all was dark eastward of it; at 8.50 a point of light a little eastward of it became visible. This point of light was very small, and apparently nearer to the west boundary of the depression than Linné is shown on my map of the Mare Serenitatis. If this point of light was the earliest illumination of Linné, the cone must be very small, scarcely larger than I Ey3, which is now smaller than represented by Lohrmann and and M. Linne is certainly smaller than 1 E 02, I estimate I E y3 to be half the diameter of IE 02, and Linné two-thirds of IE 0o. The terminator will pass over Linné on June 11, between 10 and II hours. Possessors of the first sheet of my "Catalogue of Lunar objects" including area I A ẞ, are requested to add the following, which were observed on May 15, between 8 and 10 hours, G.M.T. IA 338. An isolated mountain between Agrippa and I A 6o, shown by Schröter in T LXII, fig. 2, and by Lohrmann in both map and section I. IA 639. A peak on the S. E. border of Agrippa shown by Lohrmann only in his map and section I. IA 64°. A cleft extending from I A 841 to IA Ba1. It terminates at the northern part of the mountain, I A ß31, is a bright conspicuous object, and forks about the middle of its course. It is not shown by Lohrmann, but is well given by B. and M., on the New Edition of the large Map as a mountain ridge, forking as above described. Its character may be better determined under an earlier illumination than on the 15th of May. It is about double the width of the Hyginus cleft and brighter. It is found on De la Rue's photogram of Feb. 22, 1858. IA 641. A small mountain, N.E. of I A ẞ5. It is shown in fig. 2 of my notes and illustrations to the catalogue. Mercury is badly situated for observation, being too close to the sun, the greatest interval being three-quarters of an hour. Venus is also unfavourably situated for the same reason. Saturn may be seen almost throughout the night, but is too low to be well observed. ASTRÆEA, PALLAS, CERES. The planet Astræa comes to opposition on the 4th of the month. Date. R.A. Dec. -14 35 |