Lockyer, assisted by Mrs. Lockyer, a second; Mr. Seabroke, assisted by Mr. Burton, a third; and Mr. Pedlar a fourth. Messrs. Ranyard, Griffith, and Clifford will superintend the polariscopic observations; Messrs. Brett and Darwin will make sketches of the corona; while Messrs. Vignolles, father and son, will superintend the chronometric arrangements, and make general observations. But, probably, the most important work done at this station-if the weather is favourable-will be that superintended by Mr. Brothers, one of our most skilful photographers. Assisted by Dr. Vogel and Mr. Fryer, he hopes to obtain two series of views, one by means of one of the Sheepshanks' equatorials, belonging to the Royal Astronomical Society; the other by means of a photographic camera of his own.

I have kept to the last the strongest party of all; that, namely, which, under the charge of Dr. Huggins, proceeds to Oran, in Algeria. Here the duration of totality will be only three seconds less than the actual maximum. The name of Dr. Huggins is alone a guarantee that the spectroscopic study of the corona will not only be conducted skilfully, but with a most careful reference to strict scientific principles. He is in alliance, however, with other eminent physicists. Professor Tyndall and Dr. Gladstone are with him. Mr. Crookes joins in the spectroscopic work. Captain Noble and the Rev. F. Howlett will see that proper portions of the corona are brought upon the slit, while these two practised observers will have at the same time the opportunity of viewing the image of the corona on the screen in which the slit is made. This screen is covered with rectangular cross-lines, and the true shape of the corona will thus admit of being very readily noted. All the arrangements for viewing the spectrum of the corona and recording the place of any lines which may appear have been superintended by Dr. Huggins, at whose house I had the pleasure of inspecting them thoroughly. I cannot doubt that the actual observations-to be made severally by Dr. Gladstone and Mr. Crookes will be successful, if the weather only be favourable. Dr. Huggins himself—-after seeing before totality begins that the adjustments are properly made will devote his attention to the telescopic study of the corona. I have dwelt so much on the importance of keeping the eyes in darkness for a few minutes, at least, before totality begins, that I need hardly remark how well pleased I have been to find that so eminent a physicist and so skilful an observer intends to adopt this precaution. I attach very great importance to this feature of Dr. Huggins's plan; since very little could, I think, have been expected from the mere renewal during this eclipse of observations which have been made repeatedly during former eclipses of greater extent and importance.

The polariscopic observations at Oran are to be made by Mr. Carpenter, of the Greenwich Observatory.

As regards the results which are to be expected from these four expeditions, supposing the weather to be favourable, it does not seem to me difficult to form an opinion.

In the first place, it must not be concealed that, in this as in all former eclipse expeditions, no inconsiderable proportion of the suggested observations are likely to be of no practical utility whatever. For example, there can be no question that all the observations which are directed solely to determine whether the corona is a solar appendage will simply involve a waste of labour. It has been a misfortune that any doubts should have been started respecting a matter so thoroughly demonstrated; but this misfortune it is now too late to remedy. Nor must we forget that in former instances an even larger proportion of observing energy has been thrown away. For when, in 1860, not only England but France, Italy, Germany, and other countries sent forth their astronomers to view the Spanish eclipse, the doubts which Faye and others had urged respecting the reality of the prominences influenced more than nine-tenths of the observers. Nearly a hundred astronomers and observers endeavoured to find out whether the prominences are real solar phenomena, or mere illusions-lunar mirages, perhaps, as Faye had suggested; and it would be difficult, indeed, to say how much knowledge which, but for these illconsidered doubts, might have been acquired, was thrown away on that inauspicious occasion. The success of De la Rue and Secchi in photographing the eclipsed sun does indeed serve to render the eclipse observations of 1860 memorable, and in a sense to hide from our view the real failure of astronomers at that time. But the very success of the two who chose to work independently and usefully, only causes us to deplore the more that thirty times as many preferred to waste their energies in demonstrating the demonstrated.

On the present occasion, however, those who have pleaded for useful observations have not been wholly unsuccessful. A relatively small proportion of observing energy is to be devoted to demonstrate the abundantly demonstrated fact that the corona is a solar appendage.* Nearly all the most skilful telescopists and spectroscopists propose to inquire what the actual constitution of the corona may be, regarding its position-very

I am told that, in a recent number of "Nature," it is remarked in a leader that, "despite some hard writing to the contrary, the position of the corona remains to be proved." This is in a sense true; and so, also, it is true that every proposition of Euclid (as, for instance, Prop. 5, Book I.) remains to be proved, as far as some learners are concerned.

justly--as already established. The influence of Faye's doubts about the corona has been far less than that of his doubts about the prominences in 1860. In the plan of operations proposed for Dr. Huggins's party, in particular, one can trace no signs of any evil influence exerted by these doubts. Every suggested observation is such as will tell. The spectroscopic observations will either reveal new bright-lines in the coronal spectrum, or exhibit the Frauenhofer lines, or else prove that the spectrum really presents no other features than were seen by the American observers, Young and Pickering. The operations of Captain Noble and the Rev. F. Howlett, as auxiliaries in these observations, will be especially valuable; for we shall not only have unexceptionable evidence as to the parts of the corona actually analysed, but also full information as to the figure of the parts examined; and this, combined with Dr. Huggins's study of the structure of the corona, as seen in the telescope, can hardly fail to lead to results of the utmost interest and significance.

I should be led to attach almost equal importance to the telescopic and spectroscopic observations to be made by Mr. Lockyer's party, were it not for the unfortunate doubts which Mr. Lockyer himself entertains respecting the corona's position. One cannot fail to recognise in his instructions the effects of these doubts; the suggested observations seeming to have scarcely any other end than to solve them. There is also another strange opinion of Mr. Lockyer's, which seems almost certain to exercise an unsatisfactory influence upon the observations made by his party. He holds the chromosphere as seen by aid of the spectroscope to be only the lower portion of an envelope extending, in reality, far above the highest of the prominences. This seems to me a strange delusion. No one familiar with the history of former total eclipses can fail to recognise the fact that the outline of the chromosphere-or, as the discoverers of the layer called it, the sierra-is as well defined as that of the prominences. There is indeed not a particle of evidence tending to the belief that in eclipses it would appear otherwise than in the valuable drawings which Professor Respighi has obtained by aid of the spectroscope. Indeed, I might go much farther, and say that everything we know of the chromosphere points to the belief that it is not a solar atmosphere at all, as has been assumed, but is formed rather of small prominences and of the remains of those loftier prominences which Zöllner and Respighi have watched sinking back towards the solar surface. The gaseous envelope into which these gaseous prominences are projected to vast heights, and through which they sink slowly back, is doubtless to be regarded as the true solar atmosphere, and not that glowing

and somewhat ruddy layer whose serrated surface may be seen far below the sinking prominence-matter.

It is very probable, however, that the attempt which Mr. Brothers proposes to make to secure photographs of the corona, may cause the Sicilian party to be one of the most successful. His plan is to take a double series of photographs, one with a Sheepshanks' equatorial belonging to the Astronomical Society, the other with a camera of his own, mounted upon the equatorial and carried by the same movement. The camera pictures are intended to include a wide field, and it is far from improbable that the long coronal beams may thus, for the first time, be rendered visible in a photograph. I have had the advantage of a full discussion with Mr. Brothers of the plan he proposes to adopt, and I quite concur with him in thinking that, if weather alone be favourable, his operations are likely to be rewarded with a fuller degree of success than has yet rewarded attempts to photograph the corona.

With regard to, the long beams, I may remark that I regard them as among the most remarkable and significant phenomena presented to us by the corona. If the pictures which have been drawn by Gilman and others during recent eclipses be accepted as indicating the exact proportions of the dark and bright beams, a problem of great difficulty is presented to us. We might readily be misled by these radial beams to regard the corona as due to the passage of light-rays between the inequalities of the moon's surface, did we not attend to certain considerations which negative such a theory. Fr. Secchi, indeed, compares the corona to what is seen when the sun's light is admitted into a darkened room through a nearly circular opening imperfectly stopped by a circular plug, or through a circular opening imperfectly stopped by a nearly circular plug. Dr. Oudemann, also, has put forward a somewhat similar interpretation of the coronal beams, which he supposes due to the illumination of matter lying between the moon and earth.

When such views are studied carefully for awhile, however, fatal objections become apparent. Let us suppose for a moment-in order to give Oudemann's theory a chance, so to speak-that we may neglect that matter of the same sort which lies beyond the moon, and which, being illuminated more

* Dr. Oudemann's theory has lately been brought by Dr. De la Rue under the notice of the Astronomical Society, but was not received very favourably. Of late, indeed, Dr. De la Rue has shown, as respects such theories, a consideration for the weak which appeals strongly to our sympathies as Englishmen, however far it may be from commanding our agreement as students of astronomy.

brilliantly than the matter on this side of the moon, and presenting also a far greater depth of illuminated matter, ought to give nearly all the light seen close by the moon-let us, I say, neglect this consideration, and deal only with the matter lying between the moon and earth. Then the sun's rays, passing the rough edge of the moon and falling on this matter, would certainly produce a radial appearance, resembling very closely the corona as pictured by eclipse-observers. There would be bright radial beams and intervening narrow spaces, precisely as in the picture by Mr. W. S. Gilman, jun., in Commodore Sands' report of the American eclipse. But in order that these radial beams should extend as far as they have been actually seen during eclipses, the matter capable of being thus illuminated should extend (one may easily calculate) fully 200,000 miles from the moon towards the earth. Now, assuming with Oudemann, that this matter is the exterior part of the Zodiacal Light, there is no reason why it should not extend as far as this towards the earth, or very much farther. But, then, as the corona has been seen as well in June and July as in December and January, that is, as well when the earth is a million and a half miles beyond her mean distance as when she is as much within that distance, we are utterly prevented from supposing that the limits of this zodiacal matter lie always somewhere between the moon and earth, separated as these bodies are by less than a quarter of a million of miles. In fact, to account for the visibility of the corona in all total eclipses, we must assume that when the earth is in perihelion, the zodiacal matter extends three millions of miles or so (at least) beyond the earth. This matter, thus extending beyond the earth, ought to be visible at night in a far more conspicuous manner than the corona during totality. For, according to the theory, those particles within the quarter of a million of miles separating us from the moon which are but obliquely illuminated, and whose brilliancy is marred by the strong light continuing during even the most considerable total eclipse, are yet so conspicuously lighted up as to show the radial beams on a bright background. How much more conspicuous then should be the illumination seen towards the south at midnight, where (according to the theory) a space some three millions of miles deep, full of this matter, is illuminated directly--or as the full moon is— while the darkness of night and the black background of the sky help to render the phenomenon more conspicuous. The black shadow of the earth would indeed be thrown as a long black rift across this illuminated region of the heavens; but we know how far it would reach, and what its shape would be. Even at the moon's distance the true shadow would be but about three times the moon's diameter in breadth, while at a