The theory also that some of the nebulæ are other outlying Milky Ways, or galaxies of stars, separated by tremendous distances from our own, is interesting, and was long held as almost certain, yet we have no distinct proof either one way or the other. Many of the nebulæ may be such gatherings of countless stars outside our own, or every nebula visible may be actually part and parcel of our galaxy. Much attention has of late been paid to the arrangement of stars in the sky. The more the matter is looked into, the more plainly it is seen that stars are neither regular in size nor regular in distribution. They are not merely scattered carelessly, as it were, here, there, and anywhere, but certain laws and plans of arrangement seem to have been followed which astronomers are only now beginning dimly to perceive. Stars are not flung broadcast through the heavens, each one alone and independent of the rest. They are placed often, as we have already seen, in pairs, in triplets, in quartets, in clusters. Also, the great masses of them in the heavens seem to be more or less arranged in streams, and sprays, and spirals. So remarkable are the numbers and forms of many of these streams that the idea has been suggested, with regard to the Milky Way, whether it also may not be a vast stream of stars, like a mighty river, collecting into itself hundreds of lesser streams. The contemplation of the heavens affords no spectacle so grand and so eloquent as that of a cluster of stars. Most of them lie at such a distance that the most powerful telescopes still show them to us like star-dust. “Their distance from us is such that they are beyond, not only all our means of measurement,” says Newcomb, “but beyond all our powers of estimation. Minute as they appear, there is nothing that we know of to prevent our supposing each of them to be the center of a group of planets as extensive as our own, and each planet to be as full of inhabitants as this one. We may thus think of them as little colonies on the outskirts of creation itself, and as we see all the suns which give them light condensed into one little speck, we might be led to think of the inhabitants of the various systems as holding intercourse with each other. Yet, were we transported to one of these distant clusters, and stationed on a planet circling one of the suns which compose it, instead of finding the neighboring suns in close proximity, we should see a firmament of stars around us, such as we see from the earth. Probably it would be a brighter firmament, in which so many stars would glow, with more than the splendor of Sirius, as to make the night far brighter than ours; but the inhabitants of the neighboring worlds would as completely elude telescopic vision as the inhabitants of Mars do here. Consequently, to the inhabitants of every planet in the cluster, the question of the plurality of worlds might be as insolvable as it is to us.”