INTRODUCTION. 



THE earliest and fundamental conceptions of men respecting the ob- 

 jects with which Astronomy is concerned, are formed by familiar 

 processes of thought, without appearing to have in them any thing 

 technical or scientific. Days, Years, Months, the Sky, the Constella- 

 tions, are notions which the most uncultured and incurious minds 

 possess. Yet these are elements of the Science of Astronomy. The 

 reasons why, in this case alone, of all the provinces of human knowl- 

 edge, men were able, at an early and unenlightened period, to con- 

 struct a science out of the obvious facts of observation, with the help 

 of the common furniture of their minds, will be more apparent in the 

 course of the philosophy of science : but I may here barely mention 

 two of these reasons. They are, first, that the familiar act of thought, 

 exercised for the common purposes of life, by which we give to an 

 assemblage of our impressions such a unity as is implied in the above 

 notions and terms, a Month, a Year, the Sky, and the like, is, in 

 reality, an inductive act, and shares the nature of the processes by 

 which all sciences are formed ; and, in the next place, that the ideas 

 appropriate to the induction in this case, are those which, even in the 

 least cultivated minds, are very clear and definite ; namely, the ideas 

 of Space and Figure, Time and Number, Motion and Recurrence. 

 Hence, from their first origin, the modifications of those ideas assume 

 a scientific form. 



We must now trace in detail the peculiar course which, in conse- 

 quence of these causes, the knowledge of man respecting the heavenly 

 bodies took, from the earliest period of his history. 



