because they are no longer covered by the side views of these faculæ.'*

On September 22, 1792, Herschel observed few faculæ on the Sun and few spots, but the whole disc very much marked with roughness, like an orange, and some of the lowest parts of the inequalities blackish. On the following day he thus associates this roughness with the faculæ :- The faculæ are ridges of elevation above the rough surface.'†

On February 23, 1794, Herschel noticed an appearance which is very well illustrated in Mr. Browning's drawing of the Sun, Plate I. One of the black spots on the preceding margin, which was greatly below the margin of the Sun, had, next to it, a protuberant lump of shining matter, a little brighter than the rest of the Sun, About all the spots,' he adds, the shining matter seems to have been disturbed; and is even lumpy and zig-zagged in an irregular manner. I call the spots black, not that they are entirely so, but merely to distinguish them; for there is not one of them to-day which is not partly or entirely covered with whitish and unequally bright nebulosity or cloudiness. This in many of them comes near to an ex

Perhaps the most convincing proof we have of the fact that faculæ are elevations, is that supplied by Mr. Dawes, who actually saw a facula projecting beyond the edge of the Sun's disc.

The observation next following the above in Herschel's paper (Phil. Trans. vol. lxxxv.) is worth citing, though the fact involved is now well-known to all observers of the Sun. It runs thus:- Feb. 23, 1794. By an experiment I have just now tried, I find it confirmed that the Sun cannot be so distinctly viewed with a small aperture and faint darkening glasses as with a large aperture and stronger ones; this latter is the method I always use,'

tinction of the spot, and in others, seems to bring on a subdivision.'

On September 28, 1794, Sir William Herschel observed a spot similar in its general characteristics to that on the observation of which Wilson had based his hypothesis. There is a dark spot in the Sun on the following side. It is certainly depressed below the shining atmosphere, and has shelving sides of shining matter which rise up higher than the general surface, and are brightest at the top. The preceding shelving side is rendered almost invisible by the overhanging of the preceding elevations; while the following is very well exposed; the spot being apparently such in figure as denotes a circular form viewed in an oblique direction. Near the following margin are many bright elevations close to visible depressions. The depressed parts are less bright than the common surface. The penumbra, as it is called, about this spot is a considerable plane, of less brightness than the common surface, and seems to be as much depressed below that surface as the spot is below the plane. Hence, if the brightness of the Sun is occasioned by the lucid atmosphere, the intensity of the brightness must be less where it is depressed; for light being transparent, must be the more intense the more it is deep.'

Having thus described the most striking of his first series of observations, Herschel now proceeds to enunciate his theory respecting the solar constitution.

He remarks, in the first place, that it cannot be doubted but that the Sun has a very extensive atmo

sphere; and that this atmosphere,' he proceeds, 'consists of various elastic fluids, that are more or less lucid and transparent, and of which the lucid one is that which furnishes us with light, seems also to be fully established by all the phenomena of its spots, of the faculæ, and of the lucid surface itself. There is no kind of variety in these appearances but what may be accounted for with the greatest facility, from the continued agitation which we may easily conceive must take place in the regions of such elastic fluids.'

After dwelling on certain illustrations drawn from the clouds in our own atmosphere, which Herschel (strangely enough) regards as probably decompositions of some of the elastic fluids of the atmosphere itself,' Herschel points out that the analogy of our own atmosphere will not be less to his purpose to whatever cause the clouds may owe their origin. The lucid clouds. of the Sun, so to call them, plainly exist, because we see them; the manner of their being generated may remain an hypothesis, and mine, till a better can be proposed, 1, may stand good; but whether it does or not, the consequences I am going to draw from what has been said will not be affected by it."

It is a peculiarity of Sir William Herschel's reasoning, that it is nearly always divided very definitely into two portions, which yet many who study his writings are apt to confound. We find certain conclusions on which Sir William Herschel insists, and certain hypotheses which he simply enunciates. Respecting these last, he has perhaps as often been in the wrong as in the right, and it indicates his surprising acumen, that so even a proportion should be observed in the case of mere hypotheses. Respecting the former, I cannot recall one instance in which he has been proved to have been in error. Owing to his singular clearness of mental vision, and also in part to the extreme lucidity of

Herschel then states that he regards the spots as regions where the atmosphere is free from lucid clouds, the faculæ as regions where such clouds are more numerous than elsewhere. The penumbra being generally depressed about half-way between the level of the nucleus and that of the photosphere, must of course be fainter than other parts. No spot favourable for taking measures having lately been on the Sun,' he adds, I can only judge from former appearances that the regions in which the luminous solar clouds are formed, adding thereto the elevation of the faculæ, cannot be less than 1,843, nor much more than 2,765 miles in depth. It is true that in our atmosphere the extent of the clouds is limited to a very narrow compass; but we ought rather to compare the solar ones to the luminous decompositions which take place in our aurora borealis, or luminous arches, which extend much farther than the cloudy regions. The density of the luminous solar clouds, though very great, may not be exceedingly more so than that of our aurora borealis. For if we consider what would be the brilliancy of a space two or three thousand miles deep filled with such coruscations as we see now and then in our atmosphere, their apparent intensity, when viewed at the distance of the Sun, might not be much inferior to that of the lucid solar fluid.'

his descriptions, one is very apt to forget, when he is describing mere hypotheses, that he is not discussing established conclusions; and to this probably is due the fact that some of his warmest admirers do him the injustice of insisting as earnestly on views which he put forward simply as hypotheses, as though they had been enunciated by him as legitimate deductions from observed facts.

From the luminous atmosphere of the Sun, Herschel proceeds to the opaque body, which he surmises to be of great solidity, on account of the power it exerts upon the planets. From the phenomena of those dark spots which have been repeatedly seen in the same place, and otherwise denote inequalities in their level,' he suggests that the Sun's surface is diversified with mountains and valleys.'

Then follows that remarkable passage which every student of astronomy knows by heart; but which yet (even though we may not accept as I confess I do not-the opinions suggested in it) will well bear repetition:

The Sun, viewed in this light, appears to be nothing else than a very eminent, large, and lucid planet, evidently the first, or, in strictness of speaking, the only primary one of our system, all others being truly secondary to it. Its similarity to the other globes of the solar system with regard to its solidity, its atmosphere, and its diversified surface; the rotation upon its axis, and the fall of heavy bodies, lead us on to suppose that it is most probably also inhabited, like the rest of the planets, by beings whose organs are adapted to the peculiar circumstances of that vast globe. Whatever fanciful poets might say in making the Sun the abode of blessed spirits, or angry moralists devise in pointing it out as a fit place for the punishment of the wicked, it does not appear that they had any other foundations than mere opinion and vague surmise; but now I think myself authorised, upon