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. Volume: 12; Original Published by: American Association for the Advancement of Science in 1920 in 612 pages; Subjects: Science; Science / General; Science / History; Science / Reference; Science / Study & Teaching; Science / Philosophy & Social Aspects;