An essay on comets : in two parts. Part I. Containing an attempt to explain the phaenomena of the tails of comets, and to account for their perpetual opposition to the sun, upon the philosophical principles. Part II. Pointing out some important ends for which these tails were probably designed: wherein it is shewn, that, in consequence of these curious appendages, comets may be inhabited worlds, and even comfortable habituations; notwithstanding the vast excentricities of their orbits. The whole interspersed with observations and reflections on the sun and primary planets. By Andrew Oliver, Jun. Esq. [Four lines from Pope].