LE YERKIER AND ADAMS* PLANET. 



till then were but littlejmown in the scientific world, and not at all 

 to the general public, had discovered the existence of a new 

 planet, without ever having seen it themselves, and without its 

 having been seen by any one else, will not be soon forgotten. 



2. Nevertheless, a little reflection will show that there was not so 

 much cause for surprise in such a discovery, as there might at first 

 appear to be ; the only cause of the surprise must depend upon the 

 supposition, that the existence of such a body could only be ascer- 

 tained by the immediate evidence of the eye directed upon it ; but 

 surely cases without number will suggest themselves to every 

 one, in which not only the existence of bodies, but their haunts, 

 are ascertained otherwise than by seeing them. The sports- 

 man goes forth, attended by his hounds, in pursuit of the fox ; the 

 existence of the game is ascertained by the scent of the hounds, 

 without seeing it, and possibly at a long distance from the place 

 where it lies ; by following closely the scent which it has left upon 

 its track, its place of concealment is soon attained, and the game 

 is started. 



3. If we generalise the principles suggested by this familiar 

 illustration, we shall find that it amounts to this, that the exis- 

 tence of a body, and the place at which it is to be found, can be 

 ascertained with as much certainty and precision, by closely 

 observing the peculiar effects which that body produces upon 

 other bodies upon which it acts, and by tracing these effects, 

 as if we actually saw the body we are in quest of. It is the 

 peculiar nature of the fox to leave upon the ground on which 

 he treads an odour which characterises him. The organs of the 

 hound are so constituted as to be highly susceptible of being 

 affected by this odour, and a sufficient number of these animals 

 being started over the ground, they are trained to seek for the 

 scented track, and when found to follow it. The game is thus 

 discovered, not by the sense of sight, but by the effects which 

 it has produced upon other bodies, which themselves affect a 

 different sense. 



4. Now let us suppose it possible, that a planet moving through 

 the universe, which was never seen by any observer, should pro- 

 duce upon other planets, which are seen and observed, certain 

 effects ; that these effects can be seen and ascertained by astrono- 

 mers, and that the said astronomers can infer from the general 

 principles of their peculiar science, that these effects are such as 

 could only be produced by a planetary body, moving at a given 

 time in a given direction ; such effects would, in that case, prove 

 the existence of a planet, even though it were never seen. What 

 the scent is to the hound, these effects are to the not less sagacious 

 instincts of the astronomer. 



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