Bifocal spectacles
Lenses split in two – for seeing at a distance and reading with the same spectacles, described by Benjamin Franklin in 1784.
In a letter of 1784 Benjamin Franklin wrote that he had his two pairs of spectacles cut in half and the halves joined, so that he could see both faces and his food. Whether he himself was first is uncertain.
The spectacles show how people of the Enlightenment solved everyday problems with practical ingenuity. Later bifocals were ground from a single piece.
Materials: Glass, silver, steel or tortoiseshell
Manufacture: Two halves of differently ground lenses were joined in the same frame.
A visible dividing line across the lens.
Small, round or oval lenses in thin metal frames.
Straight sides or sliding sides on 18th-century spectacles.