Construct a retrograde Vernier scale:
During construct a retrograde Vernier to a scale of 1/5, signify inches and 10th, and 30 inches and long sufficient to read to mark distance of 11.3 inches on it.
(a) Length of primary scale = 1/5 × 30
= 6 inches.
(b) Sketch a line 6 inches long and divide it into 30 equivalent parts representing inches, consequently forming a primary scale.
(c) Set off 11 equivalent parts to the left and above the primary scale and divide it into ten equivalent parts, thus forming a vernier.
(d) All division of the vernier represents 1.1 inch. Here AB represents the essential distance.