Signedprinted inside degree circle: ENGINE DIVIDED / ARM PROTRACTOR AND GONIOMETER / Pat. July 31, 1900 / Designed by S. L. Penfield. / Made in New Haven, Conn., U.S.A.
Inscribedon protecting case: ARM PROTRACTOR AND GONIOMETER;
handwritten on the back: CLIFF FRONDEL / 9/17/23 / 94
FunctionThe purpose of crystallographic goniometry is to measure the interfacial angles of crystals to determine their type.
To determine the angle between two surfaces, one has to hold the crystal edge at the scissor opening between the card and the limb. The angle being measured is read from the scale. Such contact goniometers usually have an accuracy between 15 minutes and 1 degree, and are considerably less precise when measuring small crystals.
Historical AttributesCardboard contact goniometer in universal use by students in laboratory courses.
Primary SourcesThe instruction leaflet of a similar contact goniometer designed by Penfield is available here ).
ProvenanceProf. Clifford Frondel, Geology, Harvard University