Hand Lens 10×: a Small, Steep Lens Ground and Mounted

A 10× hand lens is a small convex lens of about 25 mm focal length: held close to the eye, its magnifying power is about a quarter of a metre divided by the focal length. Grind a small pair of discs to a steep curve as for any convex lens, then seat the convex one in a turned wooden ring with a cord to carry it. The picture: a low-power reading magnifier on a dictionary page; a 10× hand lens works the same way with a much smaller, steeper lens.