☞ 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.