264 SPECIAL RESULTS IN THE URANOLOGTCAL 



world,, on Mercator's projection, of a few inches in size, 

 could have been placed before them. 



The return of comets in closed elliptic orbits, inasmuch as 

 it is the result of the attracting force of the central body, 

 must be held to indicate their comprehension within the 

 boundary of the solar dominion. But since we are uncer- 

 tain whether comets may not hereafter appear, the major 

 axes of whose ellipses shall be found to exceed in length any 

 of those which have yet been calculated, we can only say that 

 the remotest cometary aphelion with which we are acquainted 

 marks the smallest or least distant limit which can be assigned 

 to the solar system, i.e. its minimum extension. We regard the 

 solar system, therefore, as being characterised by the visible 

 and measurable results of central forces acting within the 

 system, and by cosmical bodies (planets and comets) which 

 revolve in closed paths around the sun, and remain attached 

 to it by a direct and positive connection. The attraction 

 exerted by the sun in wider spaces beyond those returning 

 and revolving bodies on other suns or fixed stars, does 

 not belong to the considerations with which we are here 

 engaged. 



The solar domain comprehends, according to the state of 

 our knowledge at the close of the first half of the nineteenth 

 century, and arranging the planets in the order of their 

 distances from the central body 



TWENTY-TWO PLANETS. (MERCURY, VENUS, EARTH, 

 MARS; Flora, Victoria, Vesta, Iris, Metis, Hebe, Par- 

 thaiope, Irene, Astraea, Egeria, Juno, Ceres, Pallas, 

 Hygiea ; JUPITER, SATURN, URANUS, NEPTUNE.) 



TWENTY-ONE SATELLITES. (1 belonging to the 



