BOOK HI. 



INDUCTIVE INVESTIGATION. 



CHAPTEK XVIII. 



OBSERVATION. 



All knowledge proceeds originally from experience. Using 

 the name in a wide sense, we may say that experience 

 comprehends all that we fed, externally or internally — 

 the aggregate of the impressions which we receive through 

 the various apertures of perception — the aggregate con- 

 sequently of what is in the mind, except so far as some 

 portions of knowledge may be the reasoned equivalents of 

 other portions. As the word experience expresses, we go 

 through much in life, and the impressions gathered inten- 

 tionally or unintentionally afford the materials from which 

 the active powers of the mind evolve science. 



No small part of the experience actually employed in 

 science is acquired without any distinct purpose. We 

 cannot use the eyes without gathering some facts which 

 may prove useful. A great science has in many cases 

 risen from iin accidental observation. Erasnnis I'artholinus 

 thus first discovered double refraction in Iceland spar; 

 Galvaui noticed the twitching of a frog's leg ; Oken was 

 struck by the form of a vertebra ; Mains accidentally 

 examined light reflected from distant windows with a 



