Curiosities of the Sky | Page 7

this strange belt of misty light. But they are not uniformly distributed in it; on the contrary, they are arrayed in clusters, knots, bunches, clouds, and streams. The appearance is somewhat as if the Galaxy consisted of innumerable swarms of silver-winged bees, more or less intermixed, some massed together, some crossing the paths of others, but all governed by a single purpose which leads them to encircle the region of space in which we are situated.
From the beginning of the systematic study of the heavens, the fact has been recognized that the form of the Milky Way denotes the scheme of the sidereal system. At first it was thought that the shape of the system was that of a vast round disk, flat like a cheese, and filled with stars, our sun and his relatively few neighbors being placed near the center. According to this view, the galactic belt was an effect of perspective; for when looking in the direction of the plane of the disk, the eye ranged through an immense extension of stars which blended into a glimmering blur, surrounding us like a ring; while when looking out from the sides of the disk we saw but few stars, and in those directions the heavens appeared relatively blank. Finally it was recognized that this theory did not correspond with the observed appearances, and it became evident that the Milky Way was not a mere effect of perspective, but an actual band of enormously distant stars, forming a circle about the sphere, the central opening of the ring (containing many scattered stars) being many times broader than the width of the ring itself. Our sun is one of the scattered stars in the central opening.
As already remarked, the ring of the Galaxy is very irregular, and in places it is partly broken. With its sinuous outline, its pendant sprays, its graceful and accordant curves, its bunching of masses, its occasional interstices, and the manifest order of a general plan governing the jumble of its details, it bears a remarkable resemblance to a garland -- a fact which appears the more wonderful when we recall its composition. That an elm-tree should trace the lines of beauty with its leafy and pendulous branches does not surprise us; but we can only gaze with growing amazement when we behold a hundred million suns imitating the form of a chaplet! And then we have to remember that this form furnishes the ground-plan of the universe.
As an indication of the extraordinary speculations to which the mystery of the Milky Way has given rise, a theory recently (1909) proposed by Prof. George C. Comstock may be mentioned. Starting with the data (first) that the number of stars increases as the Milky Way is approached, and reaches a maximum in its plane, while on the other hand the number of nebul? is greatest outside the Milky Way and increases with distance from it, and (second) that the Milky Way, although a complete ring, is broad and diffuse on one side through one-half its course -- that half alone containing nebul? -- and relatively narrow and well defined on the opposite side, the author of this singular speculation avers that these facts can best be explained by supposing that the invisible universe consists of two interpenetrating parts, one of which is a chaos of indefinite extent, strewn with stars and nebulous dust, and the other a long, broad but comparatively thin cluster of stars, including the sun as one of its central members. This flat star-cluster is conceived to be moving edgewise through the chaos, and, according to Professor Comstock, it acts after the manner of a snow-plough sweeping away the cosmic dust and piling it on either hand above and below the plane of the moving cluster. It thus forms a transparent rift, through which we see farther and command a view of more stars than through the intensified dust-clouds on either hand. This rift is the Milky Way. The dust thrown aside toward the poles of the Milky Way is the substance of the nebul? which abound there. Ahead, where the front of the star-plough is clearing the way, the chaos is nearer at hand, and consequently there the rift subtends a broader angle, and is filled with primordial dust, which, having been annexed by the vanguard of the star-swarm, forms the nebul? seen only in that part of the Milky Way. But behind, the rift appears narrow because there we look farther away between dust-clouds produced ages ago by the front of the plough, and no scattered dust remains in that part of the rift.
In quoting an outline of this strikingly original theory the present writer should not be understood as assenting to it. That it appears bizarre is not, in itself, a reason