bodies, various systems have been invented. The Ptole* 

 male supposes the earth to be fixed in the centre of the 

 universe, round which all the heavenly bodies move, each 

 affixed to a solid sphere which moves with it : first the 

 moon, then Mercury, thirdly, Venus, next the sun, fifthly, 

 Mars, then Jupiter, seventhly, Saturn. In the eighth place 

 is the firmanent, or sphere of fixed stars ; then the crvs' 

 talline heaven; and last of all the primum mobile, which 

 is supposed to move from east to west in twenty-four 

 hours, whirling all the other spheres with it. But this 

 system, being in some respects obviously false, in 

 others utterly improbable, and likewise insufficient to 

 account for many phenomena, is now universally ex- 

 ploded. 



6. In the room of this, Ihe Copernican system is now 

 generally received, which supposes the sun to be fixed 

 in the centre, without any other motion, than that round 

 his own axis. Next him is Mercury, then Venus, thirdly, ' 

 the earth, (round which the moon 'revolves) above the 

 earth, Mars, then Jupiter, and Saturn, with their atten- 

 dant moons. This system is extremely simple and natu- 

 ral, and easily accounts for most phenomena. As to the 

 objection, that it is contrary to the testimony of our 

 senses, it is easily answered. They who are in a ship 

 seem to see the shore and the land moving along, al- 

 though it is really the ship that moves. Yet let it move 

 ever so swiftly* it displaces nothing, provided it move 

 smoothly. So neitber does the motion of the earth dis- 

 place any thing on its surface, because it is equable and 

 regular. 



Not that Copernicus was the inventor of this system. 

 It was in great part known long ago. Pythagoras taught, 

 " that the earth was carried about the sun among the 

 stars, and by turning round its axis, caused day and 

 night." Yet by degrees it sunk into oblivion, till it was 

 revived by cardinal Cusa. However the Ptolemaic sys- 

 tem still prevailed, till Nicholas Copernicus, a canon of 

 Thorn, in Polish Prussia, born in the year 1473, had re- 

 solution to examine it thoroughly, and learning enough 



