PREFACE. 



THESE Tracts were written at different times between 1796 

 and 1858. The first was inserted in the ' Philosophical 

 Transactions,' with two other Papers on Light omitted in this 

 collection. These three belong to the years 1794, 5, 6, and 7, 

 when the author was a student at the University under Pro- 

 fessors Playfair and Robison. He could have wished to 

 insert an exercise which he gave in while at the class of the 

 former in 1794, which Mr. Playfair was in the habit of show- 

 ing, as having had the good fortune to hit upon the Binomial 

 Theorem, but only by induction, as its author said in answer 

 to the Professor's question, by what means he had arrived at it. 

 He made inquiry some years ago, and found that the Pro- 

 fessor's papers had not been preserved. But he cannot pass 

 over this reminiscence of the University, nor a circumstance 

 which upon the Professor's expression of an opinion respect- 

 ing his pupil's good fortune, at once fixed his inclination for 

 mathematical studies. 



