Harper's New Monthly Magazine, No. V, October, 1850, Volume I.

by Unknown

The Sun. (From Chambers's Edinburgh Journal.)

Of all the links in the stupendous chain of the cosmos, the sun, next to our own planet, is that which we are most concerned in knowing well, while it is precisely that which we know the least. This glorious orb has always been involved in the deepest mystery. All that had been revealed to us concerning it, till very recently, was derived from the observations and deductions of the elder Herschel. His discovery of a double luminous envelopment, at times partially withdrawn from various portions of the sun's surface, afforded, on the whole, a satisfactory explanation of the numerous spots that are always seen on his disk. This glimpse merely of the external changes which happen on his surface made up the sum of our knowledge of that great luminary on which the animation of our planetary system depends! One main cause of this utter ignorance on the subject, besides its own intrinsic difficulty, lay in the comparatively slight attention it had always received from astronomers generally. No individual observer ever thought of devoting himself to the solar phenomena alone, while the public observatories confined themselves to merely observing the sun's culmination at noon, or to ascertaining the exact duration of its eclipses.

We knew, from the observations of Cassini and Herschel, that the spots on the sun's disk are not alike numerous every year; and Kunowsky particularly drew the attention of astronomers to the fact, that while in the years 1818 and 1819 very large and numerous ones appeared, some visible even to the naked eye, very few, on the contrary, and those of but trifling size, were seen in the years 1822-1824. But it was reserved for the indefatigable Schwabe of Dessau, who has devoted himself for a long series of years to this one single object, to establish the fact of these spots observing a certain periodicity. Among the results of his labors—for as yet we have only his brief announcements to the scientific world in the “Astronomical Notices”—are the following: 1. That the recurrence of the solar spots has a period of about ten years; 2. That the number of the single groups of one year varies at the minimum time from twenty-five to thirty, while in the maximum years they sometimes rise to above three hundred; 3. That with their greater abundance is combined also a greater local extension and blackness of the spots; 4. That at the maximum time, the sun, for some years together, is never seen without very considerable spots. The last maximum appears to have been of a peculiarly rich character, as, from February, 1837, till December, 1840, solar spots were visible on every day of observation; while the number of groups in the former of those years amounted to 333.

But if a single individual, by observations continued unbroken for entire decenniums, has thus revealed to us the most important fact hitherto known relating to the sun, there are other questions not less important which can only find their solution in the careful observation of a rarely-occurring interval of perhaps one or two minutes. The splendor of the sun is so amazingly great, as to preclude us entirely from perceiving any object in his immediate proximity unless projected before his disk as a darkening object. At ten, or fifteen degrees even from the sun, when this luminary is above the horizon, all the fixed stars vanish from the most powerful telescopes. We are therefore in utter ignorance whether the space between him and Mercury is occupied or not by some other denizen of the planetary system. To enable us to explore the sun's immediate proximity, we require a body that shall exclude his rays from our atmosphere, and yet leave the space round the sun open to our view. Such an object can of course be neither a cloud nor any terrestrial object, natural or artificial, since parts of the atmosphere will exist behind it which will be impinged on by the sun's rays. Only during a total eclipse can these conditions be fulfilled, and even then but for a very brief [pg 691] interval, which may still be lost to the observer through unfavorable weather or from too low a position of the sun.

Notwithstanding that this rare and precarious opportunity is the only possible one we possess of becoming better acquainted with the physical nature of the great luminary of day, astronomers never availed themselves of it for any other purpose than the admeasurement of the earth, which might have been done as well, if not better, during any planetary eclipse. This error or indifference, whichever it may have been, can not, however, be laid to the charge of our living astronomers. The 8th of July, 1842—the day on which the last total eclipse of the sun took place—witnessed the most distinguished of these assembled for the purpose of making, for the first time, observations calculated to afford us some insight into this greatest mystery of the celestial world. This eclipse was total on a zone which traversed the north of Spain, the south of France, the region of the Alps and Styria, and a portion of Austria, Central Russia and Siberia, terminating in China; so that the observatories of Marseilles, Milan, Venice, Padua, Vienna, and Ofen, all supplied with excellent telescopes, and in full activity, came within its range; while many astronomers, at whose observatories the eclipse was not visible, set out for places situated within the zone just described. Thus Arago and two of his colleagues repaired to Perpignan, Airy to Turin, Schumacker to Vienna, Struve and Sehidloffsky to Lipezk, and Stubendorff to Koerakow. Most of them were favored by the weather. Let us now see what the combined endeavors of these practiced and well-furnished observers have made us acquainted with.

First, as regards the obscurity, it was so great, that five, seven, and in some cases as many as ten stars were visible to the naked eye. A reddish light was seen to proceed from the horizon—that is, from those regions where the darkness was not total—and by this light print of a moderate size could, with a little difficulty, be read. Such plants as usually close their petals at night were seen in most places to close them also during the eclipse. The thermometer fell from 2 to 3 degrees of Reaumur, and in the fields about Perpignan a heavy dew fell. A change in the color of the light, and consequently of the enlightened objects, was noticed by many, although they were not agreed in their description of it. But this diversity may have been caused by the nature of the air at different places being probably different, and the degree of obscurity very unequal. At Lipezk, where the eclipse lasted the longest, being 3 minutes and 3 seconds, a darkness similar to that of night set in, and there the eclipse began exactly at noon.

The effect of the eclipse on the animal creation was similar to what had been observed before in the like circumstances: they ceased eating; draught animals suddenly stood still; domestic birds fled to the stables, or sought other places of shelter; owls and bats flew abroad, as if night had come on. Of three lively linnets, kept in a cage, one dropped down dead. The insect world too was greatly affected; ants stopped in the midst of their labors, and only resumed their course after the reappearance of the sun; and bees retreated suddenly to their hives. A general restlessness pervaded the animal world; and only those places which were situated more on the boundary of the zone, and where the obscurity was consequently less complete, formed an exception.

During the total eclipse, the dark moon which covered the sun's disk appeared surrounded with a brilliant crown of light or halo. This halo consisted of two concentric belts, of which the inner one was the lightest, and the external less brilliant, and gradually fading. In the direction of the line which connected the point of the commencement of the total eclipse with that of its termination, two parabolic pencils of light—some observers say several—appeared on the halo. Within it also light intervolved veins were observable. The breadth of the inner halo was from 2 to 3 minutes; that of the external one from 10 to 15 minutes; the pencils of light, on the other hand, extended as far as from 1 to 1½ degree; by some they were traced even to 3 degrees. The color of the halo was of a silvery white, and exhibited a violent undulating or trembling motion, its general appearance varying in the briefest space. The light of the halo was intensest near the covered solar rim. Its brilliance at Lipezk was so great, that the naked eye could hardly look on it, and some of the observers almost doubted whether the sun had really altogether disappeared. At Vienna, Milan, and Perpignan, on the contrary, the observers found the light of the halo resembling that of the moon toward its full. Bell, at Verona, who found time to estimate its intensity, ascertained it to be one-seventh of that of the full moon. Its first traces were noticed from 3 to 5 seconds before the entrance of the entire eclipse; in like manner, its last vestiges disappeared only some seconds after the eclipse was over. Vivid, however, as its light was, the halo cast but an extremely faint shadow. Some, indeed, who particularly directed their attention to it, could not detect any. But this might have been owing to those places on which the shadows would have fallen being faintly illumined by the reddish light of the horizon before mentioned. In other respects, during the progress of the eclipse, before and after its maximum, not the least change was observable in the uncovered part of the sun's disk. The cusps were as sharp and distinctly-marked as possible, the lunar mountains were projected on the sun's surface with the most beautiful distinctness and precision, and the color and brilliance of his disk, in the proximity of the moon's rim, were in no way diminished or altered. In short, nothing was seen which could be referred in the smallest degree to a lunar atmosphere.

All these phenomena, striking as they were, [pg 692] were such as the assembled observers were prepared for; for they were such as had already been noticed during previous eclipses of the sun. But there was one of quite a different character, as mysterious as it was novel to them. This was the appearance of large reddish projections within the halo on the dark rim. The different observers characterized it by the expressions—“red clouds, volcanoes, flames, fire-sheaves,” &c.; terms intended of course merely to indicate the phenomenon, and not in any way to explain it. The observers differed in their reports both with respect to the number of these “red clouds,” as well as to their apparent heights. Arago stated that he observed two rose-colored projections which seemed to be unchangeable, and a minute high. His two colleagues also saw them, but to them they seemed somewhat larger. A fourth observer saw one of the projections some minutes even after the eclipse was over, while others perceived it with the naked eye. Petit, at Montpellier remarked three protections, and even found time to measure one of them. It was 1-3/4 minute high. Littrow, at Vienna, considered them to be as high again as this; and stated “that the streaks were visible before they became colored, and remained visible also after their color had vanished.” The light of these projections was soft and quiet, the projections themselves sharp, and their form unchanging till the moment of their extinction. Schidloffsky, at Lipezk, thought he perceived a rose-colored border on the moon in places where these red clouds did not reach; but could not be certain of the fact, on account of the shortness of the time.