its brightest portion, the well-defined rose-coloured prominences were projected at various points of the circumference.'* But it is when we turn to the description of the corona, as seen by the naked eye, that the characteristic peculiarities resulting from the position of the observer are recognised. To the unaided eye,' says Myer, 'the eclipse presented, during the total obscuration, a vision magnificent beyond description. As a centre stood the full and intensely black disc of the Moon, surrounded by the aureola of a soft bright light, through which shot out, as if from the circumference of the Moon, straight, massive, silvery rays, seeming distinct and separate from each other, to a distance of two or three diameters of the lunar disc, the whole spectacle showing as upon a background of diffused rose-coloured light. This light was most intense, and extended furthest at about the centre of the lower limb, the position of the southern prominence. The silvery rays were longest and most prominent at four points of the circumference, two upon the upper and two upon the lower portion, apparently equidistant from each other (and at about the junctions of the quadrants designated as limbs) giving the spectacle a quadrilateral shape. The angles of the quadrangle were about opposite the north-eastern, north-western, south-eastern, and south-western points of the disc * Since both the prominences and the corona are luminous, we cannot positively conclude, from this description, that a part of the corona really lay behind the prominences; yet it is well to observe how closely the description accords with this view, or, in other words, with the view that the corona is a solar appendage. A banding of the rays, in some respects similar, has been noted as seen at the total eclipse of July 18, 1860. There was no motion of the rays; they seemed concentric.' * General Myer's description of the general aspect of the sky and air when the total eclipse was in progress deserves to be added :— The approach of the Moon's shadow,' he says, 'did not appear to be marked by any defined line, or the movement of any dark column of shade through the air. The darkness fell gradually, shrouding the mountain ranges and the dim world below in most impressive gloom. Our guides had been instructed to watch for the shadow, and to call to us at the glasses. They saw nothing of which to give notice. At the same time, and in vivid contrast, the clouds above the horizon were illuminated with a soft radiance; those towards the east with lights like those of a coming dawn, orange and rose prevailing; those northward and westward, as described to us by Mr. Charles Coale of Abingdon, Virginia, who was present, with rainbow bands of light of varied hues. I quote, in his words, a description written by him, as of interest in reference to the dispersion of light :-"The grandest of all to us, who had no astronomical ambition, or astronomical knowledge, to gratify, was the effect upon the clouds during the total obscuration. Those who have had the privilege of being upon White Top, and enjoying the westward scene, will remember the grand panoramic view of mountains beginning on the northern and southern horizon, and stretching away to the west till they seem to meet, and will appreciate the scene that we now attempt to describe. Stretching along this semicircle of mountains in long horizontal lines, far below the Sun, lay light and fleecy clouds, as if resting upon their wings during the seeming struggle between the orbs above them. At the moment of the falling of the dark shadow, when naught was to be seen above but the stars and the circle of light around the Moon, these clouds became arrayed in all the colours of the rainbow, presenting an indescribable richness with their background of sombre mountain. To our vision, it was as if bands of broad ribbon, of every conceivable hue, had been stretched in parallel lines half round the universe." In a letter subsequently written to General Myer, on the subject of the remarkable colour-scene described above, Mr. Coale remarks: 'I was probably bordering on the extravagant (though not more so than is allowable in country journalism) in giving to the clouds "all the colours of the rainbow." I clearly remember, however, that there were distinct During this eclipse a more successful attempt was made to photograph the corona than on any former From a Photograph of the Solar Corona during the Eclipse of occasion. Fig. 90 represents the corona as photographed by Mr. Whipple, of Shelbyville, Kentucky. The fourcornered aspect is here distinctly recognised, and the probability may be inferred that, with a longer exposure, the rays would have been presented as seen by Gilman, Eastman, and others, if not as seen by hands of pink, purple, yellow, orange, and fiery red, and each slightly tinged with different shades of its own colour. One of the bands had, I remember, to my vision, a slight lilac tinge. I do not remember to have observed any green or blue, but I do remember that the lower edge of the purple had a very faint blue tinge. All these resting against a dark background gave them an indescribably gorgeous appearance, the lines of colour seeming to be divided by stripes of black. They all lay in horizontal lines one above the other. My impression is, that those colours appeared at the moment the shadow passed from the lower edge of the Sun, though I am not positive.' General Myer. In the photograph there is, indeed, a sharpness of outline which might readily be interpreted by those unacquainted with the nature of photographic processes to imply the existence of a real boundary line separating this part of the corona from the part without. But, as a matter of fact, the sharpness of outline is due to peculiarities in the process of development. It may be recognised in the photographs taken at Ottumwa, although in them the corona has a much smaller extent. It is not noticed, however, in the photographs by Dr. Curtis, where the corona has about the same degree of extension; the reason being, that he employed special care in avoiding over-development of the negative. Hence no doubt whatever can remain that the sharpness of outline in the Ottumwa photographs, as also in Mr. Whipple's, implies no real limitation of the object photographed.* * As some stress has been laid on this matter by those who advocate theories respecting the terrestrial nature of the corona, it may be well to present at length Dr. Curtis's statement respecting the erroneous interpre tation of these photographic records. He says that he has read with surprise an extract from a letter, written by Dr. Gould to Professor Henry Morton, in which the former says: 'An examination of the beautiful photographs made at Burlington and Ottumwa, by the sections of your party in charge of Professors Mayer and Himes, and a comparison of them with my sketches of the corona, have led me to the conviction that the radiance around the Moon, in the pictures made during the totality, is not the corona at all, but is actually the image of what Mr. Lockyer has called the chromosphere.' 'Dr. Gould proceeds,' says Dr. Curtis, to specify the points at variance between the corona as photographed and the same object as seen and sketched by him; and because the two representations do not correspond in feature, he infers that the objects depicted cannot be identical. This same argument would apply equally well to the "radiance" shown in my own photographs, since in Such is a sketch of the evidence adduced up to the year 1870 respecting the solar corona. It appears them the phenomenon, though faint, agrees in outline with the similar object on the Burlington and Ottumwa pictures. Now, I cannot but believe that Dr. Gould is in error in imagining this aureola not to be simply the image of the more intense portion of the corona near the surface of the Sun. In the first place, the experience of this very eclipse has shown how guardedly all sketches and drawings of the appearances of totality should be received, as affording an accurate record of either the shape, size, or position of the various objects. This is evident upon comparing the various sketches made by eyeobservers of the protuberances and corona, both with each other and with the photographs, and observing the very great discrepancies manifest. Of course, it is not meant that accurate measurements made by a micrometer eye-piece in the telescope, or similar determinations of position-angle, cannot be relied upon, but, on the contrary, the argument is that only such are to be received as trustworthy, and that all general sketches and drawings made hastily during the few exciting minutes of totality, or from memory afterwards, form but a weak ground upon which to base an important scientific hypothesis. But positive proof in the question at issue is afforded by the very perfect photographs of the corona taken at Shelbyville, Kentucky, by Mr. Whipple, of the Cambridge expedition. Here we have a series of several negatives obtained by receiving the focal image of a six-inch object-glass directly upon the sensitive plate, and taken, with a wide range of exposure, from fire to forty seconds. Of these the one exposed the longest (fig. 90) yields a splendid and unmistakable picture of the corona, representing it where the converging rays occurred, of a depth equal to a quarter of the Moon's diameter. Surely Dr. Gould cannot imagine the aureole of this photograph to be the chromosphere and not the corona; and yet all these pictures of Mr. Whipple's, and all of the Philadelphia expedition, and my own, agree perfectly in the features and position of the various irregularities in the outline of the corona, the difference in the representation of that object in the several photographs being solely one of extent and brilliancy. Dr. Gould adduces, as an additional argument in favour of his assumption, the observation that the long coronal beams appeared to him to be "variable," while the "aureole" photographed was evidently "constant" during the time of totality. This argument, however, loses some of its force when it is remembered that to other observers the corona appeared to the eye absolutely unchangeable, both in form and position, during the whole period of the total obscuration.' Dr. Curtis then proceeds to consider how far Dr. Gould may have |