INTRODUCTION. 



1]ST order to the acquisition of any such exact and real knowledge ol 

 nature as that which we properly call Physical Science, it is requi- 

 site, as has already been said, that men should possess Ideas both dis- 

 tinct and appropriate, and should apply them to ascertained Facts. 

 They are thus led to propositions of a general character, which are 

 obtained by Induction, as will elsewhere be more fully explained. We 

 proceed now to trace the formation of Sciences among the Greeks by 

 such processes. The provinces of knowledge which thus demand our 

 attention are, Astronomy, Mechanics and Hydrostatics, Optics and 

 Harmonics ; of which I must relate, first, the earliest stages, and next, 

 the subsequent progress. 



Of these portions of human knowledge, Astronomy is, beyond doubt 

 or comparison, much the most ancient and the most remarkable ; and 

 probably existed, in somewhat of a scientific form, in Chaldea and 

 Egypt, and other countries, before the period of the intellectual activ- 

 ity of the Greeks. But I will give a brief account of some of the other 

 Sciences before I proceed to Astronomy, for two reasons ; first, because 

 the origin of Astronomy is lost in the obscurity of a remote antiquity ; 

 and therefore we cannot exemplify the conditions of the first rise of 

 science so well in that subject as we can in others which assumed their 

 scientific form at known periods ; and next, in order that I may not 

 have to interrupt, after I have once begun it, the history of the only 

 progressive Science which the ancient world produced. 



It has been objected to the arrangement here employed that it is 

 not symmetrical ; and that Astronomy, as being one of the Physical 

 Sciences, ought to have occupied a chapter in this Second Book, 

 instead of having a whole Book to itself (Book in). I do not pretend 

 that the arrangement is symmetrical, and have employed it only on 

 the ground of convenience. The importance and extent of the his- 

 tory of Astronomy are such that this science could not, with a view to 

 our purposes, be made co-ordinate with Mechanics or Optics. 



