SUGGESTIONS TO READERS
1. The general reader will be chiefly interested in PartsI, II, and IV.
2. Readers with a distaste for mathematics will find theessential theory stated in words in Part II.
3. Those interested in statistical analysis should readChapter XIX.
4. The Appendix to Chapter XIX contains the statisticaltables used in the analysis presented in the text.
5. The analytical table of contents, the index, and therunning page headings have been constructed withespecial reference to the varying needs of differentclasses of readers. The book presents a completetheory of interest, and it is hoped that those who ap-proach it from special viewpoints may, in the end,read it all.