This is a vintage-style, black and white engraving depicting a scientific demonstration of air pressure. A hand is shown holding an ornate glass upside down. Beneath the glass is a piece of paper, and the glass is resting on the paper without it falling through. The glass appears to be filled with water, which is contained within the glass due to the air pressure. The background is filled with dense, cross-hatched lines, creating a textured effect. The image is labeled 'Fig. 41. - Pressure of the air.'