ADVERTISEMENT. 



THIS Essay was written as a continuation of the Dissertations on the Progress 

 of Mathematical and Physical Science by Professor PLAYFAIE, and Sir JOHN 

 LESLIE, which appeared in the later Editions of the ENCYCLOPEDIA BRITANNICA. 

 It is now reprinted for general circulation, in consequence of repeated applica- 

 tions ,to that effect. Only a few inconsiderable alterations have been made upon 

 it. For information as to the plan of the Work, the reader is referred to the 

 Introductory Chapter. 



EDINBURGH, January 1858. 



299 



