It is used to amplify small variations of length.

The spherometer consists of a central steel support with an inset screw, which forms a sppike of variable height (1mm scale) and a rotaing disk fixed vertically to the screw, with graduations to measure the height of the disk on a 1/100 scale. Adjusted to the support are three spike-shaped legs at equal angles of 120degrees.

Functioning:

Made in Russia

Used at the Gymansium of Volos during the 19th century for experiments at the lessons of Physics and Chemistry.

Made in Germany.

Made in Germany
Roberval balance, see: http://www.lhup.edu/~dsimanek/museum/roberval.htm