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however, that (1) a considerable proportion of the coronal light is reflected; (2) that all the reflection does not take place in our own atmosphere; and (3) that it is not such as would result if the Sun's light were reflected from mere amorphous dust, but rather as though the reflection took place from surfaces of a crystalline nature.

But undoubtedly the most important results of the eclipse were those obtained by the aid of photography. The eclipse of December 1870 stands distinguished in fact from all other eclipses, as the first during which the corona was well rendered on glass. We have seen that Mr. Whipple had fair views in 1869, and a careful study of F. Secchi's photographs, taken in 1860, shows the corona to be really present there-very faintly traced indeed, but in a manner which we can now understand. But the only real picture of the corona as yet taken by photographic means is, beyond all question, that obtained by Mr. Brothers, at Syracuse, during the last thirteen seconds of the totality at that station. Mr. Willard, in Spain, obtained an excellent view of the inner part of the corona, but a stop or diaphragm cut off all the outer parts; so that his picture, though of great value and importance (more particularly for purposes of comparison), can by no means be regarded as a view of the corona as it really existed in the heavens at the time of the eclipse.

The explanation of Mr. Brothers's success is to be found in the fact that he adopted a new method of photographing the eclipsed sun. Hitherto a telescope

had always been employed for the purpose; but Mr. Brothers employed a photographic camera, mounted on the telescope-stand (as a matter of fact mounted on a telescope*) so as to be accurately driven by the clockwork. The object lens was a very fine one of thirty inches focal length and four inches diameter, lent to Mr. Brothers by the maker, Mr. Dallmeyer. It gave a brilliant image of the Sun about three-tenths of an inch in diameter.

Before proceeding to consider the result of Mr. Brothers's work with this instrument, it is necessary to notice that the work may be viewed in two aspectsfirst, as it relates to the question (which some regarded as still unanswered) whether the corona is a solar appendage, and secondly, in its bearing on the very difficult problem of the determination of the corona's real nature and constitution.

After what I have said in the preceding pages, and had urged in many places and ways before the eclipse expeditions sailed, it will be understood that I regard the bearing of the photographs on the first point as a matter of very slight importance.

Still, so long as the doubts and difficulties just referred to continue to be urged, it is necessary to indicate carefully any new facts which may seem to supply a more obvious (though not a sounder) answer to them than any of the facts heretofore known. The evidence

* The Sheepshanks equatorial, belonging to the Royal Astronomical Society; the same instrument which was employed by Colonel Tennant in the spectroscopic analysis of the prominences in 1868. This instrument is at present in my possession, for researches relating to the distribution of the stars.

obtained during the eclipse of December 1870 was new and striking.

In the first place, that the teaching of the photographs may be better appreciated, let us consider the evidence obtained from direct observation. This evidence is in many respects more satisfactory than

FIG. 92.

R

R'

The Corona, as drawn by Lieutenant Brown. RR', the outer
radiated corona; II', the inner and brighter corona.

during former eclipses, because the attention of the observers was directed more especially to the delineation of the corona's shape. Owing to bad weather, however, at some of the stations, the evidence from direct observations would have been incomplete—as we

shall presently see-but for the photographs of Willard and Brothers.

In Spain the corona was well seen at several stations. It was described by most of the observers as generally quadrangular in shape, but with a remarkable V-shaped gap in the lower left hand (or eastern) quadrant. The accompanying picture, by Lieutenant Brown, agrees very well with the accounts of the other observers, except that the V-shaped gap is not here shown quite so large as some considered it to have been. Lieutenant Brown, when this picture was exhibited at the January meeting of the Royal Astronomical Society,* agreed (in answer to a remark to

* It should be noticed that when this drawing was exhibited Mr. Brothers had not yet reached England, nor had any description of his photograph been received. Indeed, his negative had been carefully packed away; and in a letter addressed to me (in the middle of January), he told me he was unable to describe the position of the dark rifts until he had unpacked his negative, so little was he aware of the anxiety with which his description and drawings were expected. It has been said (with unfair significance of tone) that Lieutenant Brown had had the opportunity of studying Willard's photograph during the voyage home from Spain. But no one who compares Lieutenant Brown's view with fig. 93 will believe that the former was based on the latter. Strangely enough, the very letter in which this charge (for the insinuation involves a serious charge) was made, stated that Willard's photograph should not be placed as in fig. 92, but inverted; differing wholly, therefore, from Lieutenant Brown's, but agreeing with Lord Lindsay's photographs. Now these objections cannot both be maintained. Nor, indeed, can either. The insinuation against Lieutenant Brown is an unworthy one; and I believe there is not any evidence for it even as a possibility. I do not think any of the English observers in Spain had the opportunity of seeing Willard's photograph, which was, I know, new to several of them even so late as the January meeting of the Astronomical Society. As to the other theory, it is undoubtedly true that the best of Lord Lindsay's photographs (the only published one) cannot possibly be brought into agreement with the photographs pictured in figs. 93 and 94,

this effect) that his drawing did not quite adequately represent the dimensions of the gap.

unless either it or both of those be inverted. It is not by the corona alone (very faintly shown in Lord Lindsay's photograph), but by the prominences, that this is shown. Now Mr. Brothers is absolutely certain that his photograph has not been inverted; and the American Professors Young and Winlock have not understood that they have been mistaken in supposing that Willard's photograph is also correctly placed as in fig. 89. Their comments also, and the comments of many others, on the agreement between the two photographs have been published for many months without eliciting any correction from Mr. Willard himself. It may be fairly believed then that Mr. Willard's opinion as to the true position of the photographs agrees with that of Mr. Brothers. Further, the opinions of Mr. Willard and Mr. Brothers must be regarded as confirmed by the silence of their respective assistants. (Mr. Fryer, who worked with Mr. Brothers, is an exceedingly skilful and well-practised astronomical observer, as is Mr. Brothers himself; so that it is impossible to suppose they could misapprehend a matter depending only on the position of an instrument with which both were perfectly familiar.) Against this evidence we have the opinion of Lord Lindsay and his assistant, Mr. Davis, that their position for the photograph is the correct one. Lord Lindsay used a Newtonian reflector, of excellent construction, by Mr. Browning-an instrument admirably adapted for the work of celestial photography; but nothing is easier than to misjudge the way in which a photograph taken with such an instrument is to be viewed, in order that it may correspond with the actual aspect of the object pictured. The very circumstance which constitutes the great convenience of Newtonians (both for observation and photography) illustrates this; for the observer can look horizontally at the image of a celestial object situated anywhere in the heavens. There is reflection with inversion at the great mirror, reflec tion again with inversion at the small mirror, and then the usual inversion of the rays in passing through the eye-piece. Now, remembering that Lord Lindsay had had very little practice with his instrument, and was a comparative beginner in astronomical observation, and that Mr. Davis had had even fewer opportunities, while they worked so rapidly during the eclipse as to take no less than 9 photographs in 2 minutes, can it be doubted that the error lies with them, and not with Messrs. Willard, Fryer, and Brothers? Apart, however, from these considerations, the extended zone of prominences disclosed on the west of Mr. Brothers's photograph shows demonstrably that he has his picture properly placed; for it was taken at the end of totality, or just before the Sun's western edge was about to reappear.

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