The circles were read with a vernier scale. The position of the telescope can be read by means of an attached Vernier scale. Vernier refined this process and gave us the vernier scale. The precision-diameter gages consist of a narrow metal ribbon bearing special graduations vernier scale. He was inventor and eponym of the vernier scale used in measuring devices. In it he described the ingenious device which now bears his name, the vernier scale. It included an examination of nautical instruments and explained the recently introduced vernier scale. Twenty four spaces on the Vernier scale equal in extreme length twenty three double degrees. The vernier scale allows the user more accurately measure diameter. The circles are read using a vernier scale, accurate to about 5 minutes of arc. The movable arm has a vernier scale which permits readings of 1/16th degree.