1948. First Edition. 113 pages. Pictorial dust jacket over paper covered boards with cloth spine. Black and white photographs. Fold-out gradient diagram of line at rear. Pages with some foxing and tanning, particularly to endpapers and textblock edges. Binding remains firm. Boards have mild shelf wear with light rubbing and corner bumping. Some light marking and tanning. Unclipped jacket has heavy edge wear with tears, chipping and creasing. Rear surface detached at spine.