A slide is made to play upon it with a vernier scale, graduated to hundredths of an inch.
"Ordnance Instructions for the United States Navy." by Bureau of Ordnance, USN
NONIUS SCALE, OR VERNIER.
"The Sailor's Word-Book" by William Henry Smyth
Passing the eye up the vernier and scale, the second line above 3 is perceived to lie evenly with a line of the scale.
"A Treatise on Meteorological Instruments" by Henry Negretti
It consists of a fixed frame with scale and vernier.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 1" by Various