SUMMER, in architecture, is a large stone, the first that is laid over columns and pilasters, in beginning to make a cross vault.
&noise, in carpentry, is a large piece of timber, which, being supported on two stone piers, or posts, serves as a lintel to a door, window, &c.
SUN, in astronomy, the most conspicu ous of the heavenly bodies, which occu pies the centre of the system which com prehends the earth, the primary and secondary planets, and comets. The sun is the magnificent luminary which en lightens these worlds, and by its pre sence constitutes day. We have referred to this article from the fixed &rams, be cause the sun agrees with them in several particulars, as in the property of emit ting light continually, and in retaining constantly its relative situation, with but little variation : they may have probably many other properties in common. The sun is, therefore, justly considered as a fixed star comparatively near us ; and the stars as suns at immense distances from our earth ; and we reasonably infer, from the same analogy, that the stars are pos sessed of gravitation, and of the other general properties of matter ; they arc supposed to emit heat as wen as light ; and it has been conjectured that they serve to cherish the inhabitants of a mul titude of planetary bodies revolving round them.
In a paper on the " Constructions of the Heavens," Dr. Herschel says it is very probable, that the great stratum called the milky way, is that in which the sun is placed, though perhaps not in the centre of its thickness, but not far from the place where some smaller stratum branches from it. Such a supposition will satisfactorily, and with great simpli city, account for all the phenomena of the milky way, which, according to this hypothesis, is no other than the ap pearance of the projection of the stars contained in this stratum, and its secon dary branch. See GALAXY.
In another paper on the same subject, he says that the milky way is a most ex tensive stratum of stars of various sizes admits no longer of the least doubt ; and that our sun is actually one of the hea venly bodies belonging to it is as evi dent.
We will now, says the Doctor, retreat to our own retired station in one of the planets attending a star in the great com bination, with numberless others ; and in order to investigate what will be the appearances from this contracted situa tion, let us begin with the naked eye. The stars of the first magni tude, being in all probability the near est, will furnish us with a step to begin our scale ; setting off, therefore, with the distance of Sirius or Arcturus, for in stance, as unity, we will at present sup pose that those of the second magnitude are at double, and those of the third are treble the distance, and so forth. Tak ing it then for granted, that a star of the seventh magnitude is about seven times as far from us as one of the first, it fol lows, that an observer, who is enclosed in a globular cluster of stars, and not far the centre, will never be able, with the naked eye, to see to the end of it ; for since, according to the above estima tions, he can only extend his view about seven times the distance of Sirius, it can not be expected that his eyes should reach the borders of a cluster, which has, perhaps, not less than fifty stars in depth every where around him. The whole universe, therefore, to him, will be comprised in a set of constellations, richly ornamented with scattered stars of all sizes. Or if the united brightness of a neighbouring cluster of stars should, in a remarkably clear night, reach his sight, it will put on the appearance of a small, faint, nebulous cloud, not to be perceived without the greatest attention. Allow ing him the use of a common telescope, he begins to suspect that all the milki ness of the bright path which surrounds the sphere may be owing to stars. By increasing his power of vision, he be comes certain that the milky way is, in deed, no other than a collection of very small stars; and the nebula: nothing but clusters of stars.