Page:Popular Science Monthly Volume 58.djvu/328

320 galactic poles, as supposed by Herschel and Struve. In the language of Seeliger: "The Milky Way is no merely local phenomenon, but is closely connected with the entire constitution of our stellar system."

This conclusion is strengthened by a study of the data given by Celoria. It will be remarked that the zone counted by this astronomer cuts the Milky Way diagonally at an angle of about 62°, and, therefore, does not take in either of its poles. Consequently, regions I. and IX. are both left out. For the remaining seven regions the results are shown as follows: We show first the area, in square degrees, of each of the regions, II. to VII., included in Celoria's zone. Then follows in the next column the number of stars counted by Celoria, and, in the third, the number enumerated in the Durchmusterung in these portions of each region. The quotients show the star-density, or the mean number of stars per square degree, recorded by each authority:

It will be seen that the law of increasing star-density from near the galactic pole to the galaxy itself is of the same general character in the two cases. The number of stars counted by Celoria is generally between 18 and 25 times the number in the Durchmusterung.

An important point to be attended to hereafter is that the star-density of the Milky Way itself, as derived from each authority, is between two and three times that near the galactic poles. Very different is the result derived from the Herschelian gauges, which is this:

From the gauges of the Herschels it follows that the galactic star density is nearly 20 times that of the galactic poles. At these poles the Herschels counted about 50 per cent, more stars than Celoria. In the galaxy itself they counted 14 for every one by Celoria. The principal cause of this discrepancy is the want of uniformity of the magnitudes.

The recent comparisons of the Durchmusterung with the heavens, mostly made since Seeliger worked out the results we have given, show that the limit of magnitude to which this list extends is far from uniform, and varies with the star-density. In regions poor in stars, all of the latter to the tenth magnitude are listed; in the richer regions of the galaxy the list stops, we may suppose, with the ninth magnitude, or