SPECTACLES

, an optical machine, consisting of two lenses set in a frame, and applied on the nose, to assist in defects of the organ of sight.

Old people, and all presbytæ, use Spectacles of convex lenses, to make amends for the flatness of the eye, which does not make the rays converge enough to have them meet in the retina.

Short-sighted people, or myopes, use concave lenses, to prevent the rays from converging so fast, on account of the greater roundness of the eye, or smallness of the sphere, which is such as to make them meet before they reach the retina.

F. Cherubin, a capuchin, describes a kind of Spectacle telescopes, for viewing remote objects with both eyes; and hence called binoculi. Though F. Rheita had mentioned the same before him, in his Oculus Enoch et Eliæ. See Binocle. The same author invented a kind of Spectacles, with three or four glasses, which performed very well.

The invention of Spectacles has been much disputed. They were certainly not known to the ancients. Francisco Redi, in a learned treatise on Spectacles, contends that they were first invented between the years 1280 and 1311, probably about 1290; and adds, that Alexander de Spina, a monk of the order of Predicants of St. Catharine, at Pisa, first communicated the secret, which was of his own invention, upon learning that another person had it as well as himself.

The author tells us, that in an old manuscript still preserved in his library, composed in 1299, Spectacles are mentioned as a thing invented about that time: and that a celebrated Jacobin, one Jourdon de Rivalto, in a treatise composed in 1305, says expressly, that it was not yet 20 years since the invention of Spectacles. He likewise quotes Bernard Gordon in his Lilium Medicinæ, written the same year, where he speaks of a collyrium, good to enable an old man to read without Spectacles.

Musschenbroek observes, (Introd. vol. 2, pa. 786) that it is inscribed on the tomb of Salvinus Armatus, a nobleman of Florence, who died in 1317, that he was the inventor of Spectacles.

Du-Cange, however, carries the invention of Spectacles farther back; assuring us, that there is a Greek poem in manuscript in the French king's library, which shews that Spectacles were in use in the year 1150; however the dictionary of the Academy Della Crusca, under the word occhiale, inclines to Redi's side; and quotes a passage from Jourdon's sermons, which says that Spectacles had not been 20 years in use; and Salvati has observed that those sermons were composed between the years 1330 and 1336.

It is probable that the first hint of the construction and use of Spectacles, was derived from the writings either of Alhazen, who lived in the 12th century, or of our own countryman Roger Bacon, who was born in 1214, and died in 1292, or 1294. The following remarkable passage occurs in Bacon's Opus Majus by Jebb, p. 352. Si vero homo aspiciat literas et alias res minutas per medium crystalli, vel vitri, vel alterius perspicui suppositi literis, et sit portio minor spheræ, cujus convexitas sit versus oculum et oculus sit in aëre, | longe melius videbit literas, et apparebunt ei majores.— Et ideo hoc instrumentum est utile senibus et habentibus oculos debiles: nam literam quantumcunque parvam possunt videre in sufficienti magnitudine. Hence, and from other passages in his writings, much to the same purpose, Molyneux, Plott, and others, have attributed to him the invention of reading-glasses. Dr. Smith indeed, observing that there are some mistakes in his reasoning on this subject, has disputed his claim. See Molyneux's Dioptr. p. 256. Smith's Optics, Rem. 86—89.

SPECULATIVE Geometry, Mathematics, Music, and Philosophy. See the Substantives.

previous entry · index · next entry

ABCDEFGHKLMNOPQRSTWXYZABCEGLMN

Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

This text has been generated using commercial OCR software, and there are still many problems; it is slowly getting better over time. Please don't reuse the content (e.g. do not post to wikipedia) without asking liam at holoweb dot net first (mention the colour of your socks in the mail), because I am still working on fixing errors. Thanks!

previous entry · index · next entry

SOUTHING
SPACE
SPANDREL
SPECIES
SPECIFIC
* SPECTACLES
SPECULUM
SPHERE
SPHERICAL
SPHERICITY
SPHERICS