699 COSMOS. 



the mathematical knowledge of the Greeks, (unfortunately 

 still in manuscript,) justly comments on " the profound consi- 

 deration of nature evinced by Anaxagoras, in whom we read 

 with astonishment a passage, asserting that the moon, if its 

 centrifugal force ceased, would fall to the earth like a stone 

 from a sling. "* 



I have already, when speaking of aerolites, noticed similar 

 expressions of the Clazomenian and of Diogenes of Apollonia 

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

 clearer idea than Aristotle of the attractive force exercised by 

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

 the Stagyrite was indeed acquainted, like Hipparchus, with 

 the acceleration of falling bodies, although he did not correctly 

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

 attraction is limited to bodies having an affinity for one ano- 

 ther or, in other words, to those in which there exists a 

 tendency of the homogeneous elementary substances to combine 

 together. J John Philoponus, the Alexandrian, a pupil of Am- 

 monius, the son of Hermias, who probably lived in the sixth 

 century, was the first who ascribed the movement of the hea- 

 venly bodies to a primitive impulse, connecting with this idea 



* Pint, de facie in orbeLunce, p. 923. (Compare Ideler, Meterologia 

 veterum Grcecorum et JRomanorum, 1832, p. 6.) In the passage of 

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

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

 to all (the material) celestial bodies, is shown in Diog. Laert. ii. 12, 

 and by the many passages which I have collected (p. 122.). Compare 

 also Aristot. de Ccelo, ii. 1, p. 284, a. 24, Bekker, and a remarkable 

 passage of Simplicius, p. 491, b, 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, 

 (1. c.) " that water in a phial is not spilt when the movement of rotation 

 is more rapid than the downward movement of the water," rrj iiri TO 

 KCLTU) rov vdarog 0ap5c. 



t See Cosmos, p. 122. (Compare Letronne, Des opinions cosmogra- 

 phiques des Peres de VEglise, in the Revue des deux Mondes f 1834^ 

 Cosmos, t. i. p. 621.) 



See, regarding all that relates to the ideas of the ancients on 

 attraction, gravity, and the fall of bodies, the passages collected with 

 great industry and discrimination, by Th. Henri Martin, Etudes sur le 

 Timee de Platon, 1841, t. ii. pp. 272280, and 341. 



