SHOOTING STARS. ii09 



ceased."*' Thus we see in this simile, after the assumption 

 of a centrifugal revolution which Empedocles perceived in 

 the apparent rotation of the celestial sphere, a centripetal 

 force gradually arise as an ideal antithesis. This force was 

 specially and most distinctly described by the acute inter- 

 preter of Aristotle, Simplicius (p. 491, Bekker). He explains 

 the non-falling of the celestial bodies thus : " that the cen- 

 trifugal force predominates over the proper fall-force, the 

 drawing downward''' These are the first conjectures re- 

 specting active central forces ; and the Alexandrian, Johan- 

 nes Philoponus, a disciple of Ammonius Hermea, probably 

 of the sixth century, as it were, recognizing also the inertia 

 of matter, first ascribes " the motion of the revolutionary 

 planets to a 'primitive impulse," which he ingeniously (De 

 Creatione Mundi, lib. i., cap. xii.) unites with the idea of 

 the " fall, a tendency of all heavy and light bodies toward 

 the Earth." We have thus endeavored to show how a great 

 phenomenon of nature and the earliest purely cosmical ex- 

 planation of a fall of aerolites essentially contributed in 

 Grecian antiquity, step by step, but certainly not by math- 

 ematical reasoning, to develop the germ which, fostered by 

 the intellectual labors of the following centuries, led to Huy- 

 gens's discovery of the laws of circular motion. 



Commencing from the geometrical relations of the periodic 

 (not sporadic) falling stars, we direct our attention especially 

 to what recent observations as to the divergence or point of 

 departure of the meteors, and their entirely 'planetary ve- 

 locity, have made known. Both these circumstances, di- 

 vergence and velocity, characterize them with a high degree 

 of probability as luminous bodies which present themselves 

 independently of the Earth's rotation, and penetrate into our 

 atmosphere from ivithont, from space. The North Amer- 

 ican observations of the November period on the occasion of 

 the falls of stars in 1833, 1834, and 1837, indicated as the 

 point of departure the star y Leonis ; the observations of 

 the August phenomenon, in the year 1839, Algol in Perseus, 

 or a point between Perseus and Taurus. These centers of 

 divergence were about the constellations toward which the 

 Earth moved at the same epoch. f Saigey, who has submit- 



* The remarkable passage alluded to in the text in Plutarch, De Facia 

 in Orbe Lunoe, p. 923, is literally translated, " However, the motion of 

 the Moon and the violence of the revolution itself prevents it from fall- 

 ing, just as things placed in a sling are prevented from falling by their 

 motion in a circle." t Cosmos, vol. i., p. 118, 119 



