PEEFAOE 



Since these Lectures were written several im- 

 portant works have appeared that discuss many of 

 the points here presented. It is proper to say that 

 the outHne of the Lectures was sketched in the 

 Author's Natural Theology published in 1867 ; 

 and many of the discussions are here abridged be- 

 cause presented with fulness in that work. In 

 some places the discussion has taken the form of 

 criticism of other works. This could not be avoid- 

 ed without ignoring many scientific and practical 

 questions that are now topics of universal interest. 

 Great respect is due to the opinions of those who 

 have carefully studied any subject, but they are to 

 be accepted only when borne out by facts. The 

 necessity for independent investigation and thought 

 is constantly pressed upon us by the fact that on 

 many subjects discussed in these Lectures, the 

 most diverse views are held by able men who have 

 enjoyed equal advantages for investigation. Every 



