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Page:Popular Science Monthly Volume 18.djvu/198

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186
THE POPULAR SCIENCE MONTHLY.

showed the true radiant to be situated on the northern limit of Perseus, close to the star Eta of that constellation; and more recent determinations of a similar nature have fully corroborated that as the chief diverging center of the August meteors. Many other contemporary showers have been detected in the same region of the heavens, but the shower of Perseids recurs year after year from its accustomed point.

During the last eleven years the writer at Bristol has awaited the annual returns of this shower, and the aggregate results of observations during the interval between the 6th and 12th of August show that 2,345 meteors have been recorded, of which 1,428 belonged to the

PSM V18 D198 Shower from camelopardus aug 6 to 12.jpg
Fig. 4.—Shower from Camelopardus (96° 71°), August 6th-12th.

display of Perseids, and 917 to other minor streams of the same epoch. In 1869 the radiant was judged to be at η Persei; in 1871 at B. Camelopardi; and in 1874 at 44° 581/2°. The average position found during the last five years has been at 44° 57°; and in the diagram (Fig. 2) a number of paths near this radiant are shown. Some of the meteors appear to be slightly erratic in their directions; but this may be explained either by errors of observation or by a double or diffused radiant point, which must often occasion non-conformity in the observed flights. In 1878 two points of departure were manifest from a series of precisely fixed courses at 44° 59° and 421/2° 54°; but in 1879 the weather interrupted observations. The present year, however, afforded an exceptionally favorable opportunity to observers, and the major radiant determined by the writer was at 44° +56°, with the decided traces of a sub-radiant at 45° 60°. In 1878 Major Tupman