Optician more important and dignified. Far-sighted or aging colonial Americans imported spectacles from Europe. Spectacles were primarily for the affluent and literate colonists, who required a valuable and precious appliance. Benjamin Franklin in the 1780s developed the bifocal. Bifocal lenses advanced little in the first half of the 19th century. The terms bifocal and trifocal were introduced in London by John Isaac Hawkins, whose trifocals were patented in 1827. In 1884 B. M. Hanna was granted patents on two forms of bifocals which become commercially standardized as the "cemented" and "perfection" bifocals. Both had the serious faults of ugly appearance, fragility,
The Black Spectacles masked and disguised figure wearing black spectacles. Amazingly, the three witnesses cannot agree upon the answers to any of the questions and no one can identify the murderer. It seems as though Chesney very carefully set up the ideal conditions for someone to murder him and escape, but Gideon Fell, upon viewing the movie footage, can answer all ten questions plus the eleventh—who is the murderer? The Black Spectacles The Black Spectacles (published in the US as "The Problem of the Green Capsule", with the subtitle "Being the psychologist's murder case"), first published in 1939, is a detective story by