Professor Play/air en Malhematleal and Physical Science. 591 

 tude is greater!' The argument here sug- ducing all tlie plienomena of the universe 

 gesttfd, now that we know liow to inea- to the same law. The time was now 

 sure centrifugal force, and to compare it arrived when, from the acknowledged as- 

 wiih others, . carries den)onstrative evi- shnilation of ilie planets to the earth, this 

 dcnce with it, because that force, if the rnighc be undertaken with some reason- 

 diurnal revolution were really performed able prospect of success. No such at- 

 by the heavens, would be such, as the tempt had hitherto been made, unleas tl't 

 forces which hold together the frame of crystalline spheres or honioceniric orbs 

 thfi material world would be wholly una- of the ancients are to be considered in 



tie to resist, 

 - There are, liowever, in the reasonings 

 j.of Copernicus, some unsound parts, 

 which show, that the power of his genius 

 was not able to dispel all the clouds 

 which in that age hung over tiie human 

 ^jTiind, and that the unfounded distiiic- 



that light. The conjectures of Kepler 

 about a kind of animation^ and of orga- 

 nic structure, ivliicii pertaded ttie plane- 

 taty regions, were too vague and indefl. 

 nite, and too little asaUjgous to anything 

 known on the eaiih, to be entitled to the 

 name of a theory. To Descartes, tiiere- 



tions of the Aristotelian physics some- fore, belongs the honour of being the firs* 

 limes afforded arguments equally falla- who ventured on the solution of the most 

 . cious to him and to his adversaries. One arduous problem which the material 

 of his most remarkable physical mistakes world offeis to the consideration of phi- 

 was his misconception with respect to losophy. For this solution he songlit no 

 the parallelism of the earth's axis; to ac- other data than waller and 7mtiun, and 

 count for which, he thought it necessary with them alone proposed to explain the 

 to assumt, in addition to the earth's ro- structure and constitution of the universe. 

 tatioH on an axis, and revolution round The matter wliich he required, too, was 

 tjie sun, tlie existence of a third motion of tiie simplest kind, possessing no pin- 

 -•Itogether distinct from either of the perties but extension, impenttrability, 

 others. In this he was mistaken ; the and inertia. It was matter in the ab- 

 axis naturally retains its parallelism, and stract, without any of its peculiar or dis- 

 it would require the action of a force to tingui»hing characters. To explain thfese 

 in«ke it do otherwise. This, as Kepler characters, was indeed a part of the task 

 afterwards remarked, is a consequence of which he proposed to himself, and thus, 

 the inertia of matter ; and, for that rea- by the simplicity of his assumptions, he 

 son, he verV justly accused Copernicus added infinitely to the difficulty of tlia 

 if not being fully acquainted with his problem which he undertook to resoUe. 

 own riches. The matter thus constituted was sun- 

 The first edition of the Astroiiomia In- posed to fill all space, and its parts, botii 

 itaurata, the publication of which was great and small, to be endued with mo- 

 solicitcd by Cardinal Schoenberg, and tion in an inii.iite variety of directions. 

 • he book itself dedicated to the Pope, From the combination of these, the rec- 

 appeared in 1543, a few days before the tdineal motion of the parts become im- 

 «leath of the author. Throughout the possible ; the atoms or panicles of mat- 

 Vvhole book, the new doctrine was ad- ter were continually diverted from the 

 vanced with great caution, as if from a lines in which they had begun to move j 

 presentiment of the opposition and injus- so that circular motion and centrifug;<l 

 lice which it wns one day to experience, force originated from their actirin on one 

 At first, hoivever, the system attracted another. Thus matter canif; to be formed 

 little notice, and was rejected by the into a multitude of vortices, differing in 

 greater part even of astronomers. It extent, in velocity, and in density; the 

 lay fermenting in secret with other new more subtile parts constituting the real 

 discoveries for more than filty years, till, voitex, in which the denser bodies float, 

 by the exertions of Galileo, it was kin- and by which they are pressed, thougfi 

 died into so bright a flame as to consume not equally, on all sides. 

 (Ite philosophy of Aristotle, to alarm the Thus the universe consists of a ipuiti, 

 hierarchy of Rome, and to threaten the tude of vortices, which limit and circum. 

 existence of every opinion not founded scribe one another. The earth and the 

 «ii experience and observation. planets are bodies carried round in the 

 DESCARTES. great vortex of the solar system ; and by 

 Descartes flourisht<l in the 17th century, the pressure of the subtile matter, which 

 and has the merit of being the first who circulates with great rapidity, and great 

 undertook to give an explanation of the centrifugal force, the denser bodies, 

 celestial motions, or who formed the which have less rapidity, and less cenrri- 

 gttai a:i(l philasophic conception of le* fugal force, are torced tJu\vii totv.ilrd the 



