HYPERBOLIC ORBITS. 



illustrious author, no other bodies, save the planets and satellites 

 then discovered, were known to move under the influence of such 

 a central attraction. These bodies, however, supplied no example 

 of the play of that celebrated theory in its full latitude. They 

 obeyed, it is true, its laws, but they did much more. They dis^ 

 played a degree of harmony and order far exceeding what the law 

 of gravitation exacted. Permitted by that law to move in any of 

 the three classes of conic sections, their paths were exclusively 

 elliptical ; permitted to move in ellipses infinitely various in their 

 eccentricities, they moved exclusively in such as differed almost 

 insensibly from circles ; permitted to move at distances subordi- 

 nated to no regular law, they moved in a series of orbits at dis- 

 tances increasing in a regular progression ; permitted to move at 

 all conceivable angles with the plane of the ecliptic, their paths 

 are inclined to it at angles limited in general to a few degrees ; 

 permitted, in fine, to move in either direction, they all agreed in 

 moving in the direction in which the earth moves in its annual 

 course. 



Accordance so wondrous, and order so admirable, could not be 

 fortuitous, and, not being enjoined by the conditions of the law 

 of gravitation, must either be ascribed to the immediate dictates 

 of the Omnipotent Architect of the universe above all general 

 laws, or to some general laws superinduced upon gravitation, 

 which had escaped the sagacity of the discoverer of that principle. 

 If the former supposition were adopted, some bodies, different in 

 their physical characters from the planets, primary and secondary, 

 playing different parts and fulfilling different functions in the 

 economy of the universe, might still be found, which would illus- 

 trate the play of gravitation in its full latitude, sweeping round 

 the sun in all forms of orbit, eccentric, parabolic, and hyperbolic, 

 in all planes, at all distances, and indifferently in both directions. 

 If the latter supposition were accepted, then no other orbit, save 

 ellipses of small eccentricity, with planes coinciding nearly with 

 that of the ecliptic, would be physically possible. 



9. The theory of gravitation had not long been promulgated, 

 nor as yet been generally accepted, when the means of its further 

 verification were sought in the motion of comets. Hitherto these 

 bodies had been regarded as exceptional and abnormal, and as 

 being exempt altogether from the operation of the law and order 

 which prevailed in a manner so striking among the members of 

 the solar system. So little attention had been given to comets 

 that it had not been certainly ascertained whether they were to be 

 classed as meteoric or cosmical phenomena ; whether their theatre 

 was the regions of the atmosphere, or the vast spaces in which the 

 great bodies of the universe move. Their apparent positions in 



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