1931. Second impression. 118 pages. No dust jacket. Red cloth covered boards. Black and white diagrams throughout. Pages with some foxing and tanning, particularly to endpapers and textblock edges. Binding remains firm. A previous owner's name to front free endpaper. Small bookshop label to front pastedown. Boards have moderate shelf wear with mild bumping and fraying to corners and crushing and fraying to spine ends. All surfaces tanned and sunned, particularly spine. Some additional moderate marks and staining.