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,
Letter to M. D'Alembert on Spectacles letter can help to understand the distinction between lived-in culture and theoretical political order. Rousseau's views on the theatre are also thought to echo current concerns with global entertainment, television and Internet taking over local customs and culture. Letter to M. D'Alembert on Spectacles Letter to M. D'Alembert on Spectacles () is a 1758 essay written by Jean-Jacques Rousseau in opposition to an article published in the "Encyclopédie" by Jean d'Alembert, that proposed the establishment of a theatre in Geneva. More generally, it is a critical analysis of the effects of culture on morals, that clarifies the links between politics