Without having by any means exhausted the variety exhibited by the spiral nebulæ, let us turn to the great representative of the other species, the Orion Nebula.

In some ways this is even more marvelous than the others. The early drawings with the telescope failed to convey an adequate conception either of its sublimity or of its complication of structure. It exists in a nebulous region of space, since photographs show that nearly the whole constellation is interwoven with faintly luminous coils. To behold the entry of the great nebula into the field even of a small telescope is a startling experience which never loses its novelty. As shown by the photographs, it is an inscrutable chaos of perfectly amazing extent, where spiral bands, radiating streaks, dense masses, and dark yawning gaps are strangely intermingled without apparent order. In one place four conspicuous little stars, better seen in a telescope than in the photograph on account of the blurring produced by over-exposure, are suggestively situated in the midst of a dark opening, and no observer has ever felt any doubt that these stars have been formed from the substance of the surrounding nebula.

There are many other stars scattered over its expanse which manifestly owe their origin to the same source. But compare the general appearance of this nebula with the others that we have studied, and remark the difference. If the unmistakably spiral nebulæ resemble bursting fly-wheels or grindstones from whose perimeters torrents of sparks are flying, the Orion Nebula rather recalls the aspect of a cloud of smoke and fragments produced by the explosion of a shell. This idea is enforced by the look of the outer portion farthest from the bright half of the nebula, where sharply edged clouds with dark spaces behind seem to be billowing away as if driven by a wind blowing from the center.