ClipArt ETC
"By use of an instrument called a map measurer, set the hand on the face to read zero, roll the small wheel over the distance; now roll the wheel in an opposite direction along the graphical scale, noting the number of yards passed over. A map measurer is valuable for use in solving map problems in patrolling, advance guard, outpost, etc." — Moss, 1914

Map measurer

"By use of an instrument called a map measurer, set the hand on the face to read zero, roll the small…

"An instrument for measuring the radii of spheres; a sphere-measurer. It is of especial service to opticians in determining focal lengths, etc. of lenses. The common form consists of a vertical screwc, with a large graduated head a, a, turning in a socket supported by three legs whose hard steel points are exactly equidistant. The fixed scale b at the side, together with the graduated screwhead, makes it possible to measure with great accuracy the distance between the extremity of the screw and the plane passing through the ends of the three supports, when, for example, all the points are in contact with the surface of the sphere." —Whitney, 1889

Spherometer

"An instrument for measuring the radii of spheres; a sphere-measurer. It is of especial service to opticians…