II 



ASTRONOMY 



IN the present course of lectures, Mathematics, 

 the science of calculation, an essential element 

 in the organisation of all exact knowledge, 

 appropriately occupies the first place. But it is 

 no less appropriate that the second place should 

 be assigned to Astronomy, the earliest product of 

 man's recognition of the uniformities which under- 

 lie natural phenomena. It is, moreover, the physi- 

 cal science of widest domain, for it embraces an 

 almost limitless range of time and space. 



The data of Astronomy are observations of the 

 positions which the heavenly bodies occupy at 

 particular times, of their apparent forms, dimen- 

 sions, and of the intensity and peculiar qualities 

 of the light which they emit. Astronomy is 

 therefore primarily an observational science, and 

 a great part of the work of the practical astronomer 

 consists in devising instruments and methods which 

 will enable him to make his observations as com- 

 plete and accurate as possible. But all that these 

 observations furnish is. a series of isolated facts. 

 The relationships in which they stand one to another 

 have to be discovered by mathematical analysis 



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