Field Glass is a special form of telescope adapted for such purposes as the observation of races or the inspection of distant views. It closely resembles the ordinary opera-glass, but the latter is designed for shorter distances. The field-glass is usually binocular, consisting of two Galilean telescopes (q.v.) arranged side by side. Such glasses give erect images, whereas ordinary telescopes give inverted images. A screw-nut placed between the two tubes enables the observer to adjust the distance between object-glass and eyepiece so as to suit his particular sight.