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 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 asteroid has been studied poorly. According to modern HCM-analyses, "Benguella" is a non-family asteroid from the main belt's background population. It orbits the Sun in the inner asteroid belt at a distance of 2.1–2.7 AU once every 3 years and 9 months (1,362 days; semi-major axis of 2.41 AU).