SEQUEL TO THE EPOCH OF NEWTON. 231 



voured to give new or improved tables of most of 

 these motions. Thus were produced Delambre's 

 Tables of the Sun, Burg's Tables of the Moon, Bou- 

 vard's Tables of Jupiter, Saturn, and Uranus. The 

 agreement between these and observation is, in 

 general, truly marvellous (L). 



We may notice here a difference in the mode of 

 referring to observation when a theory is first esta- 

 blished, and when it is afterwards to be confirmed 

 and corrected. It was remarked as a merit in the 

 method of Hipparchus, and an evidence of the 

 mathematical coherence of his theory, that in order 

 to determine the place of the sun's apogee, and the 

 eccentricity of his orbit, he required to know no- 

 thing besides the lengths of winter and spring. But 

 if the fewness of the requisite data is a beauty in 

 the first fixation of a theory, the multitude of ob- 

 servations to which it applies is its excellence when 

 it is established; and in correcting tables, mathe- 

 maticians take far more data than would be re- 

 quisite to determine the elements. For the theory 

 ought to account for all the facts : and since it will 

 not do this with mathematical rigour (for observa- 

 tion is not perfect), the elements are determined, 

 not so as to satisfy any selected observations, but so 

 as to make the whole mass of errour as small as 

 possible. And thus in the adaptation of theory to 

 observation, even in its most advanced state, there 

 is room for sagacity and skill, prudence and judg- 

 ment. 



