gation of a numerous series of observations. We have therefore requested that officers on watch on board the Bonite may note, during the whole of the voyage, the hour at which a falling star may appear, its probable angular height above the horizon, and particularly, the direction of its motion. By referring these meteors to the principal stars of the constellations which they traverse, the different questions which we have indicated may be resolved at a glance. Here, then, is a subject of research which requires no trouble. It may suffice to attach our young countrymen to the subject, to remark how interesting it would be to establish the fact of the earth being a planet, from proofs derived from such phenomena as falling stars, the inconstancy of which has become proverbial. We might add, if it were necessary, that it is scarcely possible at present to imagine any other mode of explaining the astonishing appearance of bolides (fiery meteors) observed in America on the night of the 12th and 13th of November, 1833, than by supposing that, besides the large planets, there move round the sun myriads of small bodies which are not visible but when they penetrate into our atmosphere, and there become inflamed; that these asteroids (to adopt the name which Herschel long since applied to Ceres, Pallas, Juno, and Vesta,) move in some way or other in groups; that others, however, are isolated; and that the assiduous observation of these falling stars will be, at all times, the only means of enlightening us in regard to these curious phenomena. We have just mentioned the appearance of falling stars noticed in America in 1833. These meteors succeeded each other so quickly, that they could not be counted; but a moderate calculation makes their number amount to hundreds of thousands*. They were seen along the eastern side of America from the Gulf of Mexico to Halifax, from nine o'clock in the evening to sunrise, and even, in some places, in daylight, at eight o'clock in the morning. All these meteors issued from the same point of the sky, situate near y Leonis; and that, notwithstanding the altering position of this star in consequence of the diurnal movement of the sphere. This, then, is assuredly a very remarkable fact, and we shall cite another which is not less so. The shower of falling stars in 1833 took place, as we have already said, on the night of the 12th and 13th of November. In 1799, a similar shower was observed in America, by M. von Humboldt; in Greenland, by the Moravian fraternity; and in Germany, by various persons. The date is in the night between the 11th and the 12th of November. * The stars were so numerous, and appeared in so many different regions of the sky at once, that in the attempt to reckon them, nothing more than a very rough approximation could be expected. An observer at Boston compared them, when at the maximum, to half the number of flakes seen in the air during an ordinary fall of snow. At a time the phenomenon was considerably on the decrease, he counted 650 stars in 15 minutes, although he circumscribed his observations to a zone, which did not include a tenth part of the visible horizon. This number, in his opinion, was not more than two-thirds of the whole; thus there must have been 866, and in the whole of the visible hemisphere, 8660. This last number would give 34,640 stars per hour. As the phenomenon lasted seven hours, the number that appeared at Boston must have exceeded 240,000; for it must not be forgotten that the data on which these calculations are founded, were not collected till the phenomenon was considerably on the decline. In 1832 Europe, Arabia, &c., were witnesses of the same phenomenon, but on a smaller scale. The date of this appearance is again the night between the 12th and the 13th of November. This near approach to identity in the dates, authorizes us the more to invite our young navigators to watch attentively whatever may appear in the sky from the 10th to the 15th of November, since observers who were favoured with a clear atmosphere, and who watched for the phenomenon last year (1834), saw manifest traces of it on the 12th and 13th of that month*. THE ZODIACAL LIGHT.-The zodiacal light, although known for nearly two centuries, still presents a problem which has not been solved in a satisfactory manner. The study of this phenomenon is chiefly reserved, by the very nature of things, to observers placed in the equinoctial regions. They alone can decide whether Dominico Cassini had sufficiently guarded against the causes of error to which an observer is exposed in our variable climates, and whether he had sufficiently taken into account the purity of the air, when he announced in his work that the zodiacal light is constantly brighter in the evening than in the morning; that in the course of a few days its length may vary from 60° to 100°; that these variations are connected with the appearance of solar spots, in such a manner, for instance, that there must have been an absolute relation, and not merely a fortuitous coincidence, between the weakness of the zodiacal light in 1688, and the absence of every kind of spot, luminous or otherwise, on the solar disc in that same year. It appears to us, therefore, that the Academy ought to request the * Since my report was read to the Academy, M. Berard, one of the best informed officers in the French navy, has had the kindness to address to me the following extract from the journal of the brig Loiret, of which he was the commander: "On the 13th November 1831, at 4 o'clock A. M., the sky being perfectly clear, with abundance of dew, we saw a considerable number of falling stars, and luminous meteors of a large size, For upwards of three hours there could not, on an average, be fewer than two every minute. One of these meteors, which appeared in the zenith, left an enormous train in a direction from east to west, and formed a broad luminous band (equal to half the diameter of the moon), in which many of the colours of the rainbow were very distinctly seen. Its track was visible for more than six minutes. We were then on the coast of Spain, near Carthagena; the thermometer in the air, 62-6° Fahr.; barometer, 30-3 in.; temperature of the sea, 65.2°." On the 13th November 1835, a large and brilliant meteor observed by M. Millet Daubenton, fell near Belley, in the department of Ain, and burned a barn. On the same night a falling star, more brilliant than Jupiter, was observed at Lille by M. Delezenne. Thus, all these facts tend more and more to confirm the notion, that there exists a zone composed of millions of small bodies, whose orbits meet the plane of the ecliptic near the point which the earth occupies every year, from the 11th to the 13th of November. It is a new planetary world just beginning to be revealed to us. It is doubtless unnecessary for me to say, how important it would be at the present moment to inquire whether other trains of asteroids do not meet the ecliptic in points different to that in which the earth is placed about the 13th of November. This investigation would require to be made, for example, from the 20th to the 24th of April; for in 1803 (I believe it was on the 22nd of April), there were seen in Virginia and Massachusetts, from one o'clock till three in the morning, falling stars in all directions, and in such numbers, that they might be compared to a shower of rockets. Messier relates that, on the 17th June 1777 about noon, he saw during five minutes a prodigious number of black globules passing across the sun. Might not these globules be asteröids likewise? officers of the Bonite, during the whole time they remain between the tropics, and when the moon does not enlighten the horizon, to be on the watch, either after sunset or before sunrising, and take note of the constellations which the zodiacal light traverses, of the star nearest its point, and of the angular breadth of the phenomenon near the horizon, at a determined height. It is almost superfluous to add, that an account must be kept of the hours when the observations were made. The investigation of the results may be delayed without any inconvenience till the period of returning home. We are not ignorant, and we have already hinted it, that some very able minds consider these statements of Dominico Cassini as little deserving of confidence. They are unwilling to admit that sensible physical changes could operate simultaneously through such an immense extent as the zodiacal light embraces. In their opinion, these variations in intensity and length, noticed by this great astronomer, were not real, and nothing further than intermissions of the atmospheric transparency are required to account for them. It would not now, perhaps, be impossible to prove, by comparing the observations of Fatio with those of Cassini, that atmospheric variations are insufficient to explain the phenomena described by the Parisian astronomer. With respect to the objection derived from the immensity of the space in which the physical changes must operate, it has lost all its force since we have witnessed similar phenomena exhibited by Halley's comet. Our young countrymen ought therefore zealously to devote themselves to such observations as we have pointed out. The question is important, and no person can hitherto flatter himself with having definitively solved it. AURORA BOREALIS.-It is now well ascertained that there are as many displays of polar aurora in the southern hemisphere as in the arctic regions. Everything leads us to think, that the appearances of the southern aurora, and of that which we witness in Europe, follow the same laws. This, however, is mere conjecture. If a southern aurora be seen by the officers of the Bonite in the form of an arch, it will be important to notify exactly the bearings of the intersections of this arch with the horizon, and, if these cannot be obtained, the bearing of the most elevated point. In Europe, the most elevated point always appears to be situated in the magnetic meridian of the place where the observer is stationed. It has been proved by numerous researches undertaken at Paris, that all kinds of aurora borealis, even such as do not appear above our horizon, and the existence of which, consequently, we can learn only from the reports of observers in the polar regions, alter decidedly the declination of the magnetic needle, as well as its inclination and intensity. Who, then, can presume to argue from the great distance of an aurora australis, that it never disturbs the magnetism of our hemisphere? Every case in which the attention of our travellers shall make a correct memorandum of these phenomena, may at length throw some light on the question. Such arrangements have been made, that magnetic observations will be made at Paris during the whole time of the circumna vigation of the Bonite, at periods so near each other, and in such a manner, that no perturbation can take place unobserved. THE RAINBOW.-The explanation of the rainbow may be regarded as one of Descartes's most beautiful discoveries; but, still, even after the developements which Newton has furnished, it is yet incomplete. When we look attentively at this magnificent phenomenon, we perceive under the red of the interior arch several series of green and purple, forming narrow contiguous arches, well defined, and perfectly concentric to the principal arch. Of these supplementary arcs (for that is the name given to them,) the theory of Descartes and Newton takes no notice, and indeed it cannot even be applied to them. rence. The supplementary arcs appear to be an effect of luminous interfeThese interferences cannot be produced but by drops of water of a certain smallness. It is necessary also, for otherwise the phenomenon would have no brilliancy, that, besides this condition of magnitude, the drops, or at least the greater part of them, should be almost mathematically equal in their dimensions. If, therefore, the rainbows of equinoctial regions are never attended with supplementary arcs, it would be a proof that the drops of water which there issue from the clouds are of larger size, and more unequal dimensions, than in our climates. In our ignorance of the causes of rain, this fact would by no means be void of interest. When the sun is low, the upper portion of the rainbow is, on the contrary, very much elevated. It is towards this culminating region that the supplementary arcs show themselves in greatest splendour. Descending from this, their colours become rapidly fainter. In the lower regions, near the horizon, and even considerably above it, no traces of them are ever seen, at least in Europe. It follows, therefore, that rain-drops, during their vertical descent, lose the property which they at first possess; that they have no longer the conditions necessary for efficient interference, and that they increase in size. Is it not curious, it may be asked in passing, to find in an optical phenomenon, in a peculiarity of the rainbow, a proof that in Europe the quantity of rain must be so much the less the higher we place the vessel in which it is to be received*! The increase in the size of the drops, it can scarcely be 'doubted, is owing to a precipitation of humidity on their surface; this will be in proportion to the atmospheric strata through which they pass in their descent from the cold region of their origin; and which strata are warmer and warmer, as they approach the earth. It is then almost certain that, if supplementary rainbows are formed in equinoctial regions, as in Europe, they never reach the horizon; but a comparison of the angle of the height at which they cease to be seen with the angle of disappearance noticed in our climates, seems to offer a means of obtaining some meteorological results, which can be obtained by no other method at present known. In the course of a year the reservoir in the court received eight-hundredths more water that that placed on the terrace. In the Observatory at Paris, there are | first. two vessels in which rain-water is collected; one of them is on the terrace, the other in the court, 92 English feet lower than the HALOS.-In high latitudes, off Cape Horn, for example, the sun and the moon often appear surrounded by two luminous circles, which meteorologists call halos. The radius of the smallest of these circles is about 220,-that of the larger is almost exactly 46°. The first of these angular dimensions is within a little the minimum deviation which light undergoes while traversing a glass prism of 60°; the other would be given by two prisms of 60°, or by a single prism of 90°. It seems, therefore, natural to seek for the cause of halos, as Mariotte has done, in the rays refracted by floating crystals of snow, which, as every one knows, usually present angles of 60° and 90°. This theory, besides, has been rendered still more probable since the power has been acquired of distinguishing refracted from reflected light by means of chromatic polarization. It is, in fact, the colours of the first kind (refracted light) which produce the polarized rays of the halo. What, then, still remains to be known regarding this phenomenon? It is the following:-According to theory, the horizontal diameter of a halo and the vertical diameter ought to have the same angular dimension; but we are assured that these diameters are sometimes strikingly unequal. Actual measurement alone can establish this fact; for if it has happened that a judgment of the inequality in question has been formed by the naked eye only, there are not wanting sufficient causes of illusion to explain how the most experienced physicien might be deceived. The reflecting circles of Borda are admirably adapted to the measurement of the angular distances at sea. We may, therefore, without hesitation, recommend to the officers of the Bonite to apply the excellent instruments with which all of them are provided to determine the dimensions of all the halos that may appear to them to be elliptical. They will themselves perceive that the inner edge of the halo,-the only one which is distinctly defined,—is much better adapted for observation than the outer one; but they must never, with regard to the sun, neglect to indicate whether they take the centre or the edge as the term of comparison. We likewise regard it as indispensable, that, in each direction, the two rays diametrically opposite should be measured,—for certain observers have mentioned circular halos, in which, if they are to be believed, the sun did not occupy the centre of the curve. WINDS. TRADE-WINDS.-Perhaps it will excite surprise to see the tradewinds announced as still affording a subject of important investigation; but it must be remarked, that the practice of navigators has often confined them to meagre notices; with such science cannot be satisfied. Thus it is not true, whatever may have been alleged, that to the north of the equator these winds constantly blow from the north-east; and that to the south of it they blow uniformly from the south-east. The phenomena are not the same in the two hemispheres. In each plane, moreover, they change with the seasons. Daily observations of the true direction, and, as far as practicable, of the strength of the eastern winds which prevail in equatorial regions, would therefore be a useful acquisition to meteorology. The vicinity of continents, their western sides especially, modifies the trade-winds in their strength and direction. It sometimes even hap |