The image is a vintage-style diagram, likely from a scientific or technical publication. It depicts a geometric shape resembling a star or a flower with pointed petals. The central area is a dark circle, surrounded by a series of triangular petals extending outwards. The petals are outlined with thin lines, and the entire figure is shaded with a stippled effect, creating a sense of depth and dimension. Below the diagram is the caption 'Fig. 18.' In the upper left corner, there are the letters 'ARW A5'. The background is a pale yellow color, typical of aged paper.