themselves upon a question which has been the subject of multiplied and instructive discussion in our own day. 14. But to return to the subject of Nebulæ, we may further say, with the most complete confidence, that whether or not nebulous matter be generally resolvable into shining dots, it cannot possibly be true that its being, or not being so resolvable by our telescopes, depends merely upon its smaller or greater distance from the observer. For, in the first place, that there is matter, to the best assisted eye not distinguishable from nebulous matter, which is not so resolvable, is proved by several facts. The tails of Comets often resemble nebulæ; so much so that there are several known nebulæ, which are, by the less experienced explorers of the sky, perpetually mistaken for comets, till they are proved not to be so, by their having no cometary motion. Such is the nebula in Andromeda, which is visible to the naked eye.[2] But the tails and nebulous appendages of comets, though they alter their appearance very greatly, according to the power of the telescope with which they are examined, have never been resolved into stars, or any kind of dots; and seem, by all investigations, to be sheets or cylinders or cones of luminous vapor, changing their form as they approach to or recede from the sun, and perhaps by the influence of other causes. Yet some of them approach very near the earth; all of them come within the limits of our system. Here, then, we have (probably, at least,) nebulous matter, which when brought close to the eye, compared with the stellar nebulæ, still appears as nebulous. 15. Again, as another phenomenon, bearing upon the same question, we have the Zodiacal Light. This is a faint cone of light[3] which, at certain seasons, may be seen extending from the horizon obliquely upwards, and following the course of the ecliptic, or rather, of the sun's equator. It appears to be a lens-shaped envelope of the sun, extending beyond the orbits of Mercury and Venus, and nearly attaining that of the earth; and in Sir John Herschel's view, may be regarded as placing the sun in the list of nebulous stars. No one has ever thought that this nebulous appearance was resolvable into luminous points; but if it were, probably not even the most sanguine of speculators on the multitude of suns would call these points _suns_.