united in such close systems as not to leave much room for the orbits of pianets, or comets; and that consequently, on this account also, many stars, unless we would make them mere useless brilliant points, may themselves be lucid planets, perhaps unat. tended by satellites.

Postscript.-The following observations, which were made with an improved apparatus, and under the most favourable circumstances, should be added to those which have been given. They are decisive with regard to one of the conditions of the lucid matter of the sun.

Nov. 26, 1794, 8 spots in the sun, and several sub-divisions of them, were all equally depressed. The sun was every where mottled. The mottled appearance of the sun was owing to an inequality in the level of the surface. The sun was equally mottled at its poles and at its equator; but the mottled appearances may be seen better about the middle of the disc than towards the circumference, on account of the sun's spherical form. The unevenness arising from the elevation and depression of the mottled appearance on the surface of the sun, seemed, in many places, to amount to as much, or to nearly as much, as the depression of the penumbræ of the spots below the upper part of the shining substance; without including faculæ, which were protuberant. The lucid substance of the sun was neither a liquid, nor an elastic fluid; as was evident from its not instantly filling up the cavities of the spots, and of the unevenness of the mottled parts. It exists therefore in the manner of lucid clouds swimming in the transparent atmosphere of the sun; or rather of luminous decompositions taking place within that atmosphere.

[Herschel, Phil. Trans. Abridged, 1795.]

CHAP. VII.

ON THE CONSTRUCTION OF THE HEAVENS, AND THE ORGANIZATION OF THE CELESTIAL BODIES.

A KNOWLEDGE of the construction of the heavens has always been the ultimate object of my observations, and having been many years engaged in applying my forty, twenty, and large ten feet telescopes, on account of their great space-penetrating power to review the most interesting objects discovered in my sweeps, as well as those who had before been communicated to the public in the Connoissance des Temps, for 1784, I find that by arranging these objects in a certain successive regular order, they may be viewed in a new light, and, if I am not mistaken, an examination of them will lead to consequences which cannot be indifferent to an inquiring mind.

If it should be remarked that in this new arrangement I am not entirely consistent with what I have already in former papers said on the nature of some objects that have come under my observation, I must freely confess, that by continuing my sweeps of the heavens, my opinion of the arrangement of the stars and their magnitudes, and of some other particulars, has undergone a gra. dual change; and indeed when the novelty of the subject is considered, we cannot be surprised that many things formerly taken for granted, should, on examination, prove to be different from what they were generally, but incautiously, supposed to be.

For instance, an equal scattering of the stars may be admitted in certain calculations; but when we examine the milky way, or the closely compressed clusters of stars, of which my catalogues have recorded so many instances, this supposed equality of scattering must be given up. We may also have surmised nebula to be no other than clusters of stars disguised by their very great distance, but a longer experience and better acquaintance with the nature of nebulæ, will not allow a general admission of such a principle,