1931. First Edition. 222 pages. No dust jacket. Brown cloth covered boards. Black and white diagrams. Black and white frontispiece. Pages with some foxing and tanning, particularly to endpapers and textblock edges. Binding remains firm. A previous owner's name to front free endpaper. Boards have moderate shelf wear with mild bumping and fraying to corners and crushing and fraying to spine ends. Some marks and staining to surfaces. Boards are slightly bowed.