1957. First Edition. 168 pages. Paperback book with plain cover. A Scientific American Book. Pages are moderately tanned and foxed throughout. Thumb-marking present. Noticeable cracking to gutters. Binding remains firm. Water staining to some pages, including reverse of front paper cover. Paper cover has substantial wear with marks, creases, sunning, some edge and joint tears and minor spine tears. Water staining to paper covers.