CONTENTS. 



CHAPTER I. p ag e 



Introductory Remarks 1 



CHAPTER II. 



Fact of Variation 7 



As a matter of experience 8 



As probable from analogy 10 



CHAPTER III. 



Causes of Variation 19 



1. Climatal causes generally (whether dependent 



upon latitude or upon altitude) 23 



2. Temporary heat or cold, of an unusual degree ... 42 



3. Nature of the country, and of the soil 46 



4. Isolation ; and exposure to a stormy atmosphere . 70 



CHAPTER IV. 



Organs and Characters of Variation 95 



CHAPTER V. 



Geological Reflections Ill 



CHAPTER VI. 



The Generic Theory 157 



CHAPTER VII. 



Conclusion .181 



