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,
1784 Benguella and shape remain unknown. According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, "Benguella" measures between 10.48 and 16.68 kilometers in diameter and its surface has an albedo between 0.076 and 0.24. 1784 Benguella 1784 Benguella, provisional designation , is a background asteroid from the inner regions of the asteroid belt, approximately in diameter. It was discovered by South African astronomer Cyril Jackson at the Johannesburg Observatory on 30 June 1935. It was named for the city of Benguela in Angola. The low-numbered