Contact goniometer

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Related to Contact goniometer: goniometric
a goniometer having two movable arms (ab, cd), between which (at ab) the faces of the crystals are placed. These arms turn about a fixed point, which is the center of the graduated circle or semicircle upon which the angle is read off.

See also: Goniometer

References in periodicals archive ?
Because of the relatively large size of the Alto do Giz crystals, their interfacial angles could only be obtained using a hand-held contact goniometer.
Rome de l'Isle authorized two of his pupils, Arnould Carangeot (1742-1806) and Claude Lermina (1749-1806), to construct an instrument for the measurement and reproduction of crystal angles; Carangeot, accordingly, designed the prototype of a contact goniometer.
He stated that he had precisely determined different angles of several quartz crystals with his contact goniometer, had recognized the constancy of the angles between comparable crystal faces, and had related these observations to Rome de l'Isle.
The prototype of the contact goniometer invented by Carangeot consists of a graduated semicircular arc whose diameter also serves as the stationary measuring limb.
Carangeot then invented the contact goniometer in order to pursue such measurements on all of the minerals available, providing a massive amount of data that gave Rome de l'Isle's new work a solid mathematical base.