1925. Seventh edition. 190 pages. No dust jacket. Blue cloth covered boards with gilt. Black and white diagrams throughout by Lewis Baumer. Pages with some foxing and tanning, particularly to endpapers and textblock edges. Binding remains firm. Dedication to front pastedown. Boards have heavy shelf wear with bumping and fraying to corners and crushing, fraying and tearing to spine ends and edges. All surfaces tanned and sunned, particularly spine. Some additional heavy rubbing marks.