VI ADVERTISEMENT. 



a full analysis, and critical discussion, of most of the 

 recent researches in Optics. He has also to acknow- 

 ledge his obligations to M. Moigno, for the favourable 

 introduction of the former edition of the present work, 

 in the pages of the " Repertoire," to the notice of Con- 

 tinental readers. 



The form of Lectures has been abandoned ; but 

 the author fears that the style still retains more of the 

 traces of the lecture-room than is consistent with a 

 formal scientific treatise. His only aim has been to 

 present, to those who were conversant only with the 

 elements of Mathematics, a clear and connected view 

 of his attractive subject ; and he has been compelled, by 

 this limitation, to confine himself in many cases (as in 

 all that relates to the Dynamics of Light) to a general 

 account of methods, and of their results. Those who 

 desire a more exact acquaintance with the science will, 

 of course, study it in Herschel's Essay on Light, and 

 in Airy's Tract on the Undulatory Theory t of Optics. 



