602 NOTES TO BOOK X. 



latory Theory of Optics principally grew, have neither of 

 them been detected in thermotical experiments. Prof. 

 Forbes has assumed alternations of heat for increasing 

 thicknesses of mica, but in his experiments we find only one 

 maximum. The occurrence of alternate maxima and 

 minima under the like circumstances would exhibit visible 

 waves of heat, as the fringes of shadows do of light, and 

 would thus add much to the evidence of the theory. 



Even if I conceived the Undulatory Theory of Heat 

 to be now established, I should not venture, as yet, to 

 describe its establishment as an event in the history of the 

 Inductive Sciences. It is only at an interval of time after 

 such events have taken place that their history and cha- 

 racter can be fully understood, so as to suggest lessons in 

 the Philosophy of Science. 



END OF THE SECOND VOLUME. 



