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,
HMS Mermaid (1784) with two sureties, that he would not resell her and that he would break her up within 12 months from the date of sale. She was broken up at Plymouth in November 1815. HMS Mermaid (1784) HMS "Mermaid" was a 32-gun "Active"-class fifth-rate frigate of the Royal Navy, launched in 1784 and broken up in 1815. During the French Revolutionary Wars she served in the West Indies, the Channel, and the Mediterranean. During the Napoleonic Wars she first served in the Americas, but from early 1811 on, she was armed en flute and served as a troopship until she was