This is an OCR edition without illustrations or index. It may have numerous typos or missing text. However, purchasers can download a free scanned copy of the original rare book from GeneralBooksClub.com. You can also preview excerpts from the book there. Purchasers are also entitled to a free trial membership in the General Books Club where they can select from more than a million books without charge. Original Published by: The Macmillan Company in 1917 in 531 pages; Subjects: Science; Education / Teaching Methods & Materials / Science & Technology; History / General; Juvenile Nonfiction / Science & Nature / Experiments & Projects; Science / General; Science / Study & Teaching; Science / Philosophy & Social Aspects;