DISCOVERIES IN THE CELESTIAL SPACES. 308 



On considering ths different stages of the development of 

 cosmical contemplation, we are able to trace from the earliest 

 ages faint indications and presentiments of the attraction of 

 masses and of centrifugal forces. Jacobi, in his researches on 

 the mathematical knowledge of the Greeks (mifortunately stil] 

 m manuscript), justly comments on "the profound considera 

 tion of nature evinced by Anaxagoras, in whom we read with 

 astonishment a passage asserting that the moon, if its centrif- 

 ugal force ceased, would fall to the earth like a stone from a 

 sling."* 



I have already, when speakmg of aerolites, noticed similar 

 expressions of the Clazomenian and of Diogenes of ApoUonia 

 on the " cessation of the rotatory force."! Plato truly had a 

 clearer idea than Aristotle of the attractive force exercised by 

 the earth's center on all heavy masses removed from it, for the 

 Stagirite was indeed acquainted, like Hipparchus, with the 

 acceleration of falling bodies, although he did not correctly un- 

 derstand the cause. In Plato, and according to Democritus, 

 .ittraction is limited to bodies having an affinity for one an- 



universorum, ut hi uuitatem integritatemque suam sese couferant in 

 formam globi coeuutes. Quam atFeclioueai credibile est etiam Soli, 

 Luua3, caeterisque errantinm fulgoribus iuesse, ut ejus efficacia in ea 

 qua se repreesentant rotunditate permaneaiit, quae nihilominus multis 

 modis suos efficiuut circuitus. Si igitur et terra facial alios, utpote se- 

 cundum centrum (mundi), necesse erit eos esse qui similiter extrinse- 

 cus iu multis apparent, in quibus iuveuimus aunuum circuitum. Ipsa 

 denique Sol medium mundi putabitur possidere, quae omnia ratio ordi- 

 nis, quo ilia sibi invicem succedunt, et mundi totius harmonia nos do 

 cet, si modo rem ipsam ambobus (ut aiunt) oculis inspiciamus." (Co 

 pern., Ve Revol. Orb. Ccel., lib. i., cap. 9, p. 7, b.) 



* Plut., De Facie in Orbe Lutkb, p. 923. (Compare Ideler, Meteor o 

 Idgia veterum GrcEcorum et Romanorum, 1832, p. 6.) In the passage of 

 Plutarch, Anaxagoras is not named ; but that the latter applied tho 

 same theory of " falling where the force of rotation had been intermit 

 ted" to all (the material) celestial bodies, is shown in Diog. Laert., ii., 

 12, and by the many passages which I have collected (p. 122). Com- 

 pare, also, Aristot., I>e CcbIo, ii., 1, p. 284, a. 24, Bekker, and a reinarkable 

 passage of Simplicius, p. 491, Id., in the Scholia, according to the edition 

 of the Berlin Academy, where the " non-falling of heavenly bodies" is 

 noticed " when the rotatory force predominates over the actual falling 

 force or downward attraction." With these ideas, which also partially 

 belong to Empedocles and Democritus, as well as to Anaxagoras may 

 be connected the instance adduced by Simplicius (I. c), "that water 

 in a vial is not spilled when the movement of rotation is more rapid 

 than the downward movement of the water," r^f errl to kutcj tov vdaroc 



t See Cosmos, vol. i., p. 134. (Compare Letronne, Des Cpiniont 

 Cosmo graphiqnes ies Peres de VEglise,\i\ the Revolt des Deux Mond^s 

 1834, Cosmos, t. i , p. 621.) 



