The effects of a contact would be greatly modified by circumstance. Should the comet strike the earth obliquely, it would glance off, and the consequences would be partial. If the point of collision were on a continent of the globe, mountains would be hurled from their bases, and new ones would elevate their ridges towards the clouds. Were the place of meeting on either of the great oceans, some regions would be deserted, and others would be inundated by the waters of the sea. These dreadful consequences would be increased, in an indefinite proportion, if the point of contact were in the direction of the earth's centre; the meeting would be terrific; the earth's period of revolution would, in all probability, be altered, either by carrying it nearer to or farther from the sun; a different inclination of the axis might be given, and there would be a consequent change of seasons; the diurnal motion might be either accelerated or retarded, by which the length of the day would be affected; the vast continents of the globe would be again covered with the ocean, which, deserting its bed, would rush towards the new equator. Infinitely more tremendous would be the catastrophe if the earth were struck by a _retrograde comet_ in the direction of the terrestrial centre, the comet making up, by its velocity, the deficiency of mass: in this case the centrifugal force of both bodies might be annihilated,--the centripetal principle alone obeyed, and both comet and earth rush to the sun! It must, however, be stated, that the probability of such an event is all but infinitely removed: the most likely of any that is known, to effect such a consummation, is the comet of Encke, which it has been calculated would come in collision with our earth after a lapse of 219 millions of years! This calculation proceeds on the soundest principles of reasoning, and proves not so much the safety of our globe from cometary destruction, (for some comet, hitherto unseen by mortal eyes, may _now_ be winging its flight directly towards our globe,) as the astonishing powers of the mind of man, which can thus essay to penetrate the veil of futurity, and read the destiny of a world. But destruction to this terrestrial orb and its teeming inhabitants, may be more speedily brought about than by a concussion with these celestial agents. A single principle of motion annihilated, evaporation suspended, or a component part of the atmosphere abstracted, and "final ruin would drive her ploughshare o'er creation;" universal conflagration would instantly ensue from the separation of the oxygen from the nitrogen of the atmosphere,--the former exerting its native energies without control wherever it extends,--solid rocks, ponderous marble, metals, and even water itself, would burst into an intensity of flame, and change the aspect of all sublunary things.