108 COSMOS. 



Small Planets. 



Egeria 2'579 



Juno 2-669 



Ceres 2768 



Flora 2-202 



Victoria 2-335 



Vesta 2-362 



Iris 2-385 



Metis 2-386 



Hebe 2-425 



Parthlnope 2.448 



Irene 2553 



Astrea 2-577 



Pallas 1-773 



Hygeia 3-151 



Jupiter 5-20277 



"Saturn 9-53885 



Uranus 19*18239 



Neptune 30-03628 



The simple observation of rapidly diminishing periods of 

 revolution, from those of Saturn and Jupiter to Mars and 

 Venus, led, at a very early time, under the assumption that 

 the planets were attached to movable spheres, to conjectures 

 as to the distances of these spheres from each other. As 

 there are no traces of methodically-instituted observations 

 and measurements to be found among the Greeks before the 

 time of Aristarchus of Samos, and the establishment of the 

 Alexandrinian Museum, a great difference arose in the hypoth- 

 esis as to the arrangement of the planets and their relative 

 distances ; whether according to the most prevailing system, 

 with reference to their distances from the Earth as the fixed 

 center, or, as among the Pythagoreans, with reference to the 

 distances from the focus of the universe. The principal sub- 

 ject on which there was a discrepancy of opinion was the 

 position of the Sun, that is, its relative situation in reference 

 to the inferior planets and the Moon.^ The Pythagoreans, 

 who considered number to be the source of all knowledge, the 

 real essence of all existing things, applied their theory of num- 

 bers, the all-blending doctrine of numerical relations, to the 

 geometrical consideration of the five regular bodies, to the 

 musical intervals of tone which determine, accord, and form 

 different kinds of sound, and even to the system of the uni- 

 verse itself, supposing that the moving, and, as it were, vi- 

 brating planets, exciting sound-waves, must produce a spher- 

 al music, according to the harmonic relations of their inter- 

 vals of space. • " This music," they add, "would be perceived 



* BOckh, De Platonico Syst., p. xxiv., and in Philolaos, p. 100. The 

 succession of the planets, which, as we have just seen (page 94, note), 

 gave rise to the naming of the week-days after the planetary deities, 

 that of Geminus is distinctly called the oldest by Ptolema)us. (Almag., 

 xi., cap. i.) He blames the motives from which ** the moderns haM^ 

 placed Venus and Mercury beyond the Sun." 



