sity must have been so feeble that they were merged in the general illumination of the field."

"Soon after the middle of the totality," he proceeds, "there appeared on the sun's eastern edge a fine group of prominences formed of jets, rather low, but very bright, some rectilinear, others curved round the sun's limb, and exhibiting the intricate deviations and all the characters of prominences in the neighborhood of solar spots. The brightness and color of these jets were so vivid as to give them the appearance of fireworks. The spaces between some of the jets were perfectly dark, so that the red zone of the corona appeared to be entirely wanting there." (It will be remembered that the red images of the prominences, and the red image of the corona, were necessarily accordant in position, since they were produced by the same kind of light, the red hydrogen rays.) "Perhaps, however, this was only the effect of contrast due to the extraordinary brightness of the neighboring jets. I have thought it right, however, to refer to the peculiarity because the appearance of interstices or double spaces, between prominences of considerable brightness, is often observed by means of the spectroscope independently of total eclipses. The green and red zones of the corona were well developed on the western as well as on the eastern edge of the sun, while the blue remained faint and ill defined."

It seems tolerably clear that Respighi saw, in the green image, the full extension of the inner corona; for the edge of that image was well defined, as it would certainly not have been if the observed extension had depended only on the observer's power of recognizing faint luminosity. In the latter case there would have been a gradual fading off, precisely as in the case of the blue image. It is important to notice this point; because Mr. Lockyer (probably observing under less favorable conditions) could only trace the green image of the inner corona to a height of about two minutes, or less than one third of the height observed by Respighi; and we might be led to infer that as Respighi saw the green coronal image extending so much farther from the sun than as observed by Lockyer, so under yet more favorable circumstances the image might have appeared higher still. The well-defined outline recognized by Respighi renders

this inference inadmissible; and we may in fact regard the extension of the inner corona as definitely determined by his observations. On the other hand, the relatively small extension of the blue image does not necessarily prove that the blue light does not emanate from the whole of the inner corona, since the ill-defined nature of the image affords reason for believing that its observed extension was merely a question of eyesight.

We have then-and the result can not but be regarded as one of the most important ever established during eclipses-the conclusion that surrounding the sun to a depth of nearly two hundred thousand miles, there is an envelope of hydrogen mixed with an element capable of emitting the green light so often referred to in the above description..

But we are led to pause in order to inquire what element it is which supplies the green light. Now here we have a most interesting question to consider. For the light of our own auroras shows this very green line. Professor Young has tested the matter in a way which prevents all possibility of doubt. Using a spectroscope of almost unmatched power, he could recognize no difference of position between the green line of the aurora, the green line of the inner corona, and a green line seen always in the spectrum of iron. But of all elements in the universe iron seems to be precisely the element which ought not to be present, either in the regions whence comes the light of our auroras, or in the inner corona of the sun. Iron in the solid state might indeed be present from time to time in the upper regions of our air, because iron is nearly always present in meteorites, and meteorites are always passing through the upper regions of the air in greater or less numbers. But the green line, if it in truth appertains to the iron spectrum, implies the existence of the glowing vapor of iron; and heat of great intensity is required to vaporize iron. It is, however, possible that electrical discharges may be in question. We know, indeed, that the aurora is an electrical phenomenon, although we do not as yet know exactly how the electrical action is caused, or what its nature may be. We should certainly find many difficulties obviated if we extended the same explanation to the solar corona, since many of the phenomena which it presents

are strikingly suggestive of electrical action. Viewing the green light in this way, and not venturing at present to determine the precise manner in which electrical action is excited, we should be led to recognize the presence of iron in the corona, the iron not being in the state of vapor, but giving the vapor spectrum of iron on account of the electrical discharges continually taking place between the particles of solid or liquid iron. It might even be that the hydrogen lines from the corona may be referred to electrical action, and not to the actual heat of the hydrogen present throughout the inner corona. In this way we may obviate a difficulty referred to above when the sierra was described. We may regard the sierra as the region where the sun's hydrogen atmosphere actually glows with the intensity of its own heat; and the inner corona as the region where the same atmosphere is traversed by continual electrical discharges, which cause the bright lines of the hydrogen to be recognized by our spectroscopists, though not with the same brightness as from the region of actually glowing hydrogen.*

A difficulty remains in the fact that the spectrum of iron contains upwards of four hundred and fifty bright lines, and that the green line in question is not even the most conspicuous of these. Nor, indeed, is it absolutely certain that this particular line, though always seen in the spectrum of iron, belongs actually to that metal. At present, however, the most probable conclusion appears to be that which has been presented above; and we may suppose either that the other lines of iron are really present, but too faint for recognition, or that their absence is due to the special circumstances under which iron exists in

* It should be explained that if an electrical discharge passes from iron to iron through hydrogen, the observed spectrum is a combination of the iron spectrum and the hydrogen spectrum. Now the actual brightness of light in this case is not inferior to that of hydrogen glowing with intensity of heat; but the total quantity of light is less than that which would be obtained if the

whole of the hydrogen in the tube were so glowing. In like manner, the supposed electrical discharges in the sun's hydrogen atmosphere would produce a light as intense in itself as that of the sierra; but as the discharges would cause portions only of the inner corona to glow with this light, the total luminosity would be far inferior to

the luminosity of the sierra, where all the hydrogen is aglow with its own heat.

the upper regions of our own air and in the rare hydrogen atmosphere of the sun.

In our journey outwards from the sun's light surface, we have now approached the inner boundary of the most interesting of all the solar surroundings, the outer radiated corona, the reality of which had been so long disputed. Respecting this appendage-occupying a space enormously greater than any structure known to astronomers-the recent eclipse observations have supplied most interesting information.

Let us in the first place consider the actual appearance of this object as seen under the favorable circumstances of the late eclipse. The following description is taken from a series of interesting letters which appeared in the columns of the Daily News:

"There in the leaden-colored utterly cloudless sky," he writes, "shone out the eclipsed sun! a worthy sight for gods. and men. There, rigid in the heavens, was what struck every body as a decoration-one that emperors might fight fora thousand times more beautiful than the Star of India (even where we are now)— a picture of surpassing loveliness, and giving one the idea of serenity among all the activity that was going on below; shining with a sheen as of silver essence, built up of rays almost symmetrically arranged round a bright ring, above and below, with a marked absence of them right and left, the rays being composed of sharp radial lines, separated by furrows of markedly less brilliancy."

It is very interesting to notice the greater extension of the corona above and below. For at Bekul where the observations were made the sun was close to the horizon, and his equatorial zone was nearly upright or vertical, so that the observation shows that the extension of the radiated corona is greatest opposite the sun's equatorial regions. It is worthy of notice that Father Secchi had considered this fact to be apparent in the photographs which he obtained during the eclipse of the sun in 1860.

Let us next consider the work of a practiced draftsman, Mr. Holiday.

"This gentleman," says the Daily News correspondent, "proposed to sketch with his right eye while the left was at the eyepiece of the telescope; and more than On the appearthis he did it. ance of Baily's beads," (that is, at the mo

ment when the last fine sickle of direct sunlight broke up into small arcs of light,) "he removed the dark glass from the eyepiece of his telescope, but replaced it instantly, finding that even the feeble light was still too strong for the eye that had firmly resolved to note each delicate feature of the corona. Still, the time was not lost, for in that momentary glance he saw doubtless what have been called the 'rays before totality,' which he at once recognized as the two great lines which marked the limits of the advancing shadow. After a few seconds the glass was removed, and there in all its glorious beauty was a grand corona of the most fantastic type, not unlike the one given by Liais. To outline this was the work of a few seconds. Curiously enough there are points of difference and points of agreement between this drawing and the photographs, which will, doubtless, when the time comes, undergo the most searching examination. After the middle of the eclipse another drawing was made, showing that the corona had become much more diffuse than at its first appearance, and maintained the same form nearly till the re-appearance of the sun."

It is to be noted, as respects this account, that the picture by Liais of the corona as he saw it during the eclipse of 1858, is one which has been ridiculed as altogether a work of the imagination. It presents the corona with peculiarities of detail so remarkable, that if we regard them as real, they dispose. finally of the theory that the outer corona is merely due to the illumination of our own atmosphere. Accordingly, the advocates of the atmospheric theory had scouted the pretensions of Liais's picture; and even many who regarded the corona as a solar appendage, could scarcely believe that some of the strange figures shown in the picture were not to some extent idealized. Here, however, we have such figures reproduced by a gentleman whose skill in draftmanship will hardly be questioned, and who has not advocated any theory of the coro

na.

We venture to take exception to the remark that the corona had become more diffuse by the middle of the totality; for, it is to be remembered that, with the progress of totality, the observer's power of appreciating faint light would naturally increase, and that accordingly he would be enabled to recognize those outer and

fainter parts of the corona which had in the first instance escaped his notice.

The consideration of circumstances such as these causes us to attach so much the more value to the photographic records of the eclipse, which are not liable to be affected by physiological peculiarities. From the moment when totality begun, the pho tographic plates were set one after another to record the aspect of the corona, without any fear that the plates exposed earlier or later would be more or less sensitive to the influence of the corona's very delicate light. The photographs represent the corona as unchanged in form throughout the totality, with persistent rifts, extending to a great distance from the sun. This is, in effect, decisive. There was room for a shadow of doubt (at least in some minds) when, in December, 1870, Mr. Brothers obtained, in the last eleven seconds of totality, a picture showing well-marked rifts in an extensive corona,* for there were no sufficient means of proving that the same rifts existed at the beginning of the totality. But now all doubts of that sort are finally disposed of; and since radial beams in our own atmosphere, or produced by the passage of the sun's light past the irregularities of the lunar surface, must inevitably have changed markedly in position during the progress of totality, we have decisive evidence against the two theories urged against the existence of the outer solar corona as an objective and circumsolar reality.

But the recent eclipse has also supplied instructive evidence respecting the nature of the outer radiated corona.

Mr. Janssen's remarks on this point are not wanting in definiteness; and they are particularly valuable because he observed the corona from a station raised far above those denser atmospheric strata which are most effective in concealing the more delicate details of the coronal structure:

"I have mounted the central ridge of the Neilgherries," he wrote, " which has

Mr. Brother's picture showed the corona widest on the west, whereas a picture by Lord Lindsay seemed to show the corona widest on the circumstance. But on a careful examination of east; and great importance was attached to the the prominences shown in the two pictures, it became clear that one of the pictures had been by some accident inverted. So soon as the pictures were so placed that the prominences were brought into agreement, the corona was found to extend toward the same side in each.

summits of nine thousand feet in height, and whence, according as we turn to east or west of the ridge, we see the Carnatic plains on the Coromandel Coast, or the plateau of Mysore, as far as the Ghausts." At this fine station, Janssen was favored with weather of exceptional clearness; and altogether it is probable that never since eclipse observations began, had the corona been studied under such favorable circumstances. In the following sentences Janssen presents the results of his general observations :

"Nothing could be more beautiful or more luminous; with special forms excluding all possibility of a terrestrial origin. The result of my observations at Sholoor," he says, "indicates without any doubt the solar origin of the corona, and the existence of substances beyond the chromatosphere. I think the question whether the corona is due to the terrestrial atmosphere is disposed of, (tranchée,) and we now have before us the prospect of the study of the extra-solar regions, which will be most interesting and fruitful."

In the spectroscopic study of the corona Janssen achieved a noteworthy success. Hitherto astronomers had failed in recognizing on the faint rainbow-tinted spectrum forming a background, as it were, to the distinctive bright-line spectrum of the corona, those dark lines which are seen in the spectrum of solar light. The inference was that very little or none of the coronal light is reflected sunlight. Janssen, however, besides detecting several bright lines which had not hitherto been recognized, saw also the chief solar dark lines. Strangely enough, he appears to infer from their presence that the corona exercises an absorptive effect on light which would otherwise produce a rainbow-tinted spectrum unstreaked by dark lines. To us, the more natural explanation appears to be that a portion of the coronal light is due simply to the reflection of sunlight from the cosmical matter undoubtedly surrounding the sun. Janssen himself recognizes the existence of such matter, since in his remarks on his observations he says, "Besides the cosmical matter independent of the sun, which must exist in his neighborhood, the observations de

monstrate the existence of an excessively rare atmosphere, mainly of hydrogen, extending far beyond the chromatosphere and prominences, and deriving its supplies from the very matter of the latter, matter projected (as we daily witness) with such extreme violence."

The eclipse revealed nothing, directly, respecting matter outside the coronal radiations. But indirectly, it gave important evidence respecting a solar appendage which attains a far greater extension. We refer to that strange object, the zodiacal light, emitted by a region which surrounds the sun on all sides, to distances exceeding the orbit-ranges of the planets Mercury and Venus, even if this region do not reach far beyond the orbit of our own earth. It happens, by a strange chance, that the astronomer Liais, whose longdoubted observations of the corona have just been so strikingly confirmed, has but now announced his discovery of the fact that the zodiacal light, when analyzed with the spectroscope, gives a faint continuous spectrum. It had been asserted that the zodiacal light gives a spectrum resembling that of the aurora; but grave doubts had been entertained respecting the accuracy of the observations on which this assertion had been based. The observation made by Liais would tend to show that, as had been long suspected, the zodiacal light is sunlight reflected from cosmical matter traveling continually around the sun (for we could not expect the solar dark lines to appear in so faint a spectrum.) If this is the case, the radiated corona can not but be regarded as only the innermost partthe core, so to speak-of the zodiacal region. Hence we should be led to recognize the existence of envelope after envelope around the sun, until even the vast distance at which our earth travels is reached or overpast. We need wonder little that under these circumstances our earth should sympathize with the disturbances affecting, from time to time, the great central luminary of our system, or that her frame should be thrilled from pole to pole by magnetic tremors, when his orb is excited either by internal throes, or by external impulses, to intense electrical action.

[From Good Words.