Accession No
1114
Brief Description
spectacles, periscopic, 1900 (c)
Origin
Maker
Class
optical
Earliest Date
1900
Latest Date
Inscription Date
Material
metal (steel, brass?); glass
Dimensions
length 116mm; breadth 35mm
Special Collection
Provenance
Transferred from the Cavendish Laboratory, University of Cambridge, probably from 10/1951. Probably adapted at the Cavendish Laboratory.
Inscription
‘0-11’
Description Notes
Steel frames; U bridge; round frames; double hinged side pieces with loop ends. Single lens; wider at top than at bottom. Engraved ‘0’, ‘1’, ..., ‘11’. Brass (?) rim inside frame.
Condition: fair; incomplete (one lens missing?).
References
Events
Description
Spectacles
Usually consisting of a pair of lenses held in a frame, spectacles may have originated in the ancient civilizations of China and the Mediterranean, but early forms were crude. It was only in the 18th century that the grinding of lenses became sufficiently advanced to make then really effective for correcting sight defects. In order to correct for near sightedness, the lenses must be concave, which diverges the rays of light (angles them apart), and for long sightedness they must be convex, to angle the rays of light together.
Spectacles are not solely used for defective eyesight; the Inuit and the Yupik use wooden spectacles with very small slits in them to reduce the glare from snow and ice.
FM:42573
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