the nebular hypothesis, as it was thought highly improbable that the central condensation should arise merely from the grouping of stars.
As individual stars are not scattered equally throughout space, so the groups which they form have far from a uniform distribution. There are certain regions of the heavens much richer in nebulæ than others. In the northern hemisphere, the great region of nebulæ is near the pole of the galactic circle, or the part furthest removed in every direction from the Milky Way. In the southern hemisphere, the distribution is much more uniform.
We see, then, the aggregating power ascending by a series of steps till an elevation is attained, which makes the mind giddy to contemplate. The lowest term in this ascending series is the revolution of the satellite round the planet. The next is the revolution of the planet round the sun. Then comes the stellar grouping, by which each sun in its galaxy revolves round the centre of gravity of the whole, there being many intermediate steps formed by double stars and higher combinations. It had been attempted by Maedlar to prove that our firmament revolves round the bright star Alcyone in the Pleiades. The proof is, however, by no means satisfactory. A higher step still is presented by the revolution of one galaxy round another. No such revolution has been actually observed; but double nebulæ are found in such numbers, that the same reasoning; holds in their case as in that
