PORTION OF THE COSMOS. THE PLANETS. 333 



lity seeing the high degree of intellectual cultivation of 

 the Egyptian nation, and its early construction of calendars 

 that similar measurements had been made at least as early 

 in the Valley of the Nile; but none such have come 

 down to us. Even the Peruvians although they had made 

 less advances than the Mexicans and the Muyscas (inhabi- 

 tants of the mountains of New Granada) in the improve- 

 ment of calendars and intercalation had gnomons in which 

 the style was surrounded by a circle drawn upon a very even 

 surface. These gnomons were placed in the interior of the 

 great temple of the Sun at Cuzco, as well as in many other 

 parts of the Peruvian empire : the one at Quito, situated 

 almost directly under the equator, used to be decorated with 

 flowers at festivals held at the equinoxes, and was regarded 

 with particular honour ( 534 ) . 



9. Excentricity of the planetary orbits. The form of 

 the elliptic orbits is determined by the greater or less dis- 

 tance of the two foci from the centre of the ellipse. This 

 distance or the degree of excentricity of the planetary 

 orbits expressed in parts of their semi-axes varies from 

 0*006 in Yenus (differing, therefore, very little from a circle) 

 and 0-076 in Ceres, to 0*205 in Mercury and 0-255 in 

 Juno. The least excentric orbits are successively those of 

 Yenus, Neptune, and the Earth, the last of which is now 

 diminishing at the rate of 0*00004299 in a hundred years, 

 while the minor axis is increasing; then follow Uranus, 

 Jupiter, Saturn, Ceres, Egeria Yesta, and Mars. The most 

 excentric orbits are those of Juno (0*255), Pallas (0*239), 

 Iris (0*232), Yictoria (0'217), Mercury (0*205), and Hebe 

 (0'202). In some planets as Mercury, Mars, and Jupiter 

 the excentricities are increasing; while in others as 



