Sea, between Teneriffe and Cadiz. These long trains of light are maintained by Newton, to be a thin vapor, raised by the heat of the Sun from the Comet. If we knew their uses in our System, we could form more probable conjectures as to the chronology of their creation. They have been noticed from the earliest era of our Astronomical History, and if our modern Philosophers had not discovered, that some (at least,) leave us to return again into our System, and therefore describe a vast elliptical orbit round our Sun, we might have fancied that the periods of their first recorded appearances in our field of science, were the eras of their individual formation. But their recurring presence proves, that their first existence ascends into unexplored and unrecorded antiquity. Yet, from whence they came to us, we as little know as for for what purpose. Tycha Brache proved that they were further from the Earth than the Moon, and were nearly as distant as the planets. The Comet of 1682, re-appeared in 1759, in the interval described, an orbit in the form of an ellipsis, answering to a revolution of 27,937 days. It will therefore re-appear in November, 1835. In its greatest distance, it is supposed not to go above twice as far as Uranus. This is indeed a prodigious sweep of space, and it has been justly observed, that the vast distance to which some Comets roam, proves how very far the attraction of the Sun extends; for though they stretch themselves to such depths in the abyss of space, yet by virtue of the Solar power, they return into its effulgence. But it has been recently discovered, that three Comets (at least,) never leave the planetary system. One whose period is three years and a quarter, is included within the orbit of Jupiter; another of six years and three quarters, extends not so far as Saturn; and a third of twenty years, is found not to pass beyond the circuit of Uranus. The transient effect of a Comet passing near the Earth, could scarcely amount to any great convulsion, but if the Earth were actually to receive a shock by collision, from one of those bodies, the consequences would be awful. A new direction would be given to its rotatory motion, and the Globe would revolve around a new axis. The Seas, forsaking their ancient beds, would be hurried by their centrifugal force to the new equatorial regions; islands and continents, the abodes of men and animals, would be covered by the universal rush of the waters to the new Equator, and every vestige of human industry and genius at once destroyed. Although the orbits of all the planets in the Solar System be crossed by five hundred different Comets, the chances against such an event however, are so very numerous, that there need be no dread of its occurrence; besides, that Almighty arm which first created them, and described for them their various orbitsthat Omnipotent Wisdom which directed the times of their periodical revolutions, still continues to guide and protect all the workmanship of his hands. Interrogations for Section Second. Of what does the SOLAR SYSTEM Consist? In what direction do they move in their orbits? What is the form of the orbits described by the planets? Where is the Sun placed? In what time does he turn round on his own axis? How is that proved? What is his diameter ? What is his mean apparent diameter as seen from the Earth? How is his solidity calculated?. What is the Ecliptic ? What is meant by the Nodes ? Which is the Ascending Node? Which is the Descending Node? What additional Astronomical discoveries were made in the year 1805? What planet is nearest the Sun ? What reasons are given to suppose that this planet receives its light from the Sun ? What is the computed distance of Mercury from the Sun ? What is its diameter ? In what time does it perform a revolution around the Sun ? What time on its own its axis ? How many miles does it move in an hour in its motion round the Sun? How many degrees is his orbit inclined towards the Ecliptic? What planet is next to Mercury? What is the distance of this planet from the Sun? How many miles in an hour, does Venus move in performing her revolution round the Sun ? In what time does she perform her annual revolution? In what time does she perform a revolution on her axis ? What is her diameter ? How is it known that the orbits of Mercury and Venus are included within that of the Earth? How many degrees at most does Mercury depart from the Sun ? How many Venus ? What is meant by inferior conjunction ? What is a transit ? What is the name of the third planet from the Sun ? What is its distance from the Sun? What is its diameter ? In what time does it perform a revolution around the Sun ? What is its hourly progress? In what time does it perform a revolution on its axis? What is its form? How many miles difference in the two diameters? What is the Moon? In what time does she perform a revolution round the Sun ? Around the Earth? Around her own axis? What is her distance from the Earth? How many miles in diameter? What is her mean apparent diameter as seen from the Earth? Do the orbits of the Earth and Moon coincide? How much more light does the Earth give to the Moon, than the Moon gives to us? What is the name of the fourth planet from the Sun ? What is his distance from that luminary? In what time does he perform his annual revolution? What is his hourly progress? What time his revolution on his axis? What is his mean apparent diameter as seen from the Earth? What as seen from the Sun? For what is the planet Mars remarkable? What have Astronomers concluded to be the cause of this remarkable appearance? What is its form? What is the name of the fifth planet from the Sun ? By whom was it discovered? And when? In what sign of the Ecliptic can this planet be seen without the aid of a telescope? What is its distance from the Sun ? |