1950. Fourth Edition. 338 pages. No dust jacket. Red cloth boards with gilt lettering. Contains black and white plates and folded diagrams. Clean pages and plates with light tanning and mild foxing throughout. Minor tanning to free endpapers due to dust jacket flaps. Binding remains firm. Boards have mild edge-wear with slight rubbing to surfaces and bumping to corners. Gilt lettering is darkened. Moderate sunning to spine and edges with crushing to spine ends. Moderate splits to spine and corners causing cloth to be frayed. Visible wear marks to boards.