Excerpt from Transactions of the Kansas Academy of Science, 1873 A few words with regard to the resistance of a medium, and I close. Only the orbits of short-period comets have been determined with any approach to accuracy; and of these, Encke's has the least perihelion distance. This comet, too, has a shortening of its period, apparently in consequence of the resistance of the medium through which it passes. Is it not probable, too, that such a resistance is the explanation of some of the irregularities of the comets of long period? Thus the comet of 1264 and 1556 was expected to return in 1848. May it not be that the comet of 1843 was the identical one with its period shortened? The comet of 1843 passed very near the sun; nearer even than Encke's comet. Arago made a study of the records of Halley's comet, to determine if possible whether in its successive reappear ances it had lost any of its brilliancy. He thought it had lost nothing. May not this again be due to the probable fact that in successive returns the comet approaches nearer the sun, encounters more and more of the resistance of the medium, and therefore tends to develop more fully the phenomena of the tail, which would otherwise be less developed, because the nucleus must be losing some of its volatile elements? Thus questions of interest press upon us, and astronomy, though the oldest of the sciences, is ever opening new and attractive fields of study. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.