Transcriber's Note:
- Minor typographical errors have been corrected without note.
- Punctuation and spelling were made consistent when a predominant form was found in this book; otherwise they were not changed.
- Ambiguous hyphens at the ends of lines were retained.
- The Mountain Sheep illustration has been moved from page 75 to page 74.
- Duplicated chapter headings have been omitted.
- The Contents table was added by the transcriber.