The Danville Quarterly Review Volume 1 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1861 edition. Excerpt: ... compel it to fall towards the center of our system. The form of the orbit described by such masses would depend to some extent on the perturbing influence of the planets. (4.) The phenomena of comets have made known the existence of a cosmical force of repulsion; that is, of a force directly opposed to gravitation. Sir John Herschel and other astronomers found that gravitation alone could not account for all the appearances presented by the comet of Halley in 1835. The same is true in regard to some of more recent date, and particularly that of Donati. (5.) The occasional near approach of Encke's comet to Jupiter and Mercury has enabled astronomers to correct the evaluations of the masses of those planets. Encke, soon after his discovery of the short period of this body, found that its observed perturbations could not be reconciled with the value of Jupiter's mass which was then universally received. The mass of that planet was accordingly recomputed by different astronomers, and by various methods, each resulting in a value considerably greater than that which had been adopted by Laplace. On several accounts this correction is one of great importance. (6.) The motions of this comet have indicated, moreover, the existence of a resisting medium. After taking into consideration the disturbing effect of all the known members of our planetary system, the comet ha3 been found at each successive return to anticipate its predicted perihelion passage. In other words, its period is gradually diminishing. This result might seem, at first sight, directly the reverse of that which would result from the comet's moving through an ethereal medium. Such a resistance, however, by diminishing the tangential velocity, diminishes also the centrifugal force....