Spectacles were not worn until about 1300, though the optical effects of magnifying glasses had long been observed. Among those who contributed to the development of spectacles were the Italian Salvino degli Armatis, who died in 1317, and the Englishman Roger Bacon, who died in 1294. The first eyeglasses were balanced precariously on the nose, tied to the ears with string, or held temporarily before the eyes by hand. Frames made of horn were common during the 14th to 16th centuries. In the 19th century rimless glasses and frames of gold appeared. During the 20th century frames for glasses have been made of various synthetic plastics. Bifocals, made of two segments of lens of different focal length cemented together, were in use in England during the late 18th centurv. In fact, Benjamin Franklin had bifocals constructed for himself to be worn during his travels. Though nearsightedness and farsightedness had been early recognized, it was not until 1800 that the blurred vision due to astigmatism was noticed and corrected. Astronomer Sir George Airy was one of the first to grind cylindrospherical lenses that would correct this defect in his own eyes. Contact lenses were first used in 1888 in France. The liquid used at the time to separate the glass from the eye caused great irritation, and so the use of such glasses was abandoned. Recently new methods have again led to their adoption.