174 



THE ORBIT OF URANUS. 



It will be remembered that the observed declinations have, as far as possible, 

 been reduced to Auwers' standard. We have no positive proof that this standard 

 is correct. If it be affected by a constant error, the result will be that the orbit 

 of the planet on the celestial sphere, as deduced from observation, instead of being 

 a great circle, as we know the real orbit to be, will be a small one, and the com- 

 parison of a uniform series of observations extending through an entire revolution 

 of the planet, after making the best correction to the position of the orbit, will 

 leave a constant residual. Now, we can best determine this residual by including 

 it as an unknown quantity in our equations. 



