SIGHT 425 SiGISMUND Subsequently he settled in New York City, where he entered politics; was made col- lector of internal revenue in May, 1871;
FRANZ SIGEL register of the city in October, 1871, and pension agent in 1886; later was head of an advertising bureau and editor and pub- lisher of the "New York Monthly." Died August, 1902. SIGHT, in physiology, one of the five human senses, having for its organ the Eye (q. v.). In this organ, then, we have the retina, an expansion of the optic nerve, to receive and transmit Jto the brain the impressions of light; certain refract- ing media for so disposing the rays of light traversing them as to throw a cor- rect image of an external body on the retina ; and a contracting diaphragm, with central apertures for regulating the quan- tity of light admitted into the eye. When the eye is directed to any object, an image of that object is depicted on the back of the eye by means of the rays of light en- tering the pupil, and duly refracted by the different humors. The image, which is inverted, produces, somehow, an im- pression on the retina with the assistance of the choroid coat, and this impression passes inward to the nervous centers, whence the optic nerve takes its rise. The subject of binocular vision, or that with two eyes we only perceive one object, was long a perplexing subject to philosophers, till it was satisfactorily explained by means of that now well-known instrument the Stereoscope (q. v.). The power of adapting the eye to vision at different distances has received the most varied explanations; but the opinion now generally entertained is that it de- pends mainly on some alteration, either in position or form, which takes place in the crystalline lens. Some persons pos- sess this power of adaptation in a very slight degree, and thus labor under de- fective vision, of which there are two kinds. Nearsightedness (myopia) is caused by anything — such as undue convexity of the cornea — which increases the refract- ing power of the eye, and. so causes the image of an object to be formed at a point anterior to the retina, and is rem- edied by the use of concave glasses. Long-sightedness (hypermetropia), on the other hand, is owing to conditions the re- verse of this, and is remedied by the use of convex glasses, which diminish the focal distance of an image formed in the eye. We judge of the motion of an object partly from the motion of its image over the surface of the retina, and partly from the motion of our eyes following it; and of the form of bodies, partly from the mere sensation, and partly from the as- sociation of ideas. In law, bills of exchange are frequently drawn payable "at sight" (i. e., on pre- sentation), or a certain number of days "after sight." In the last case the time begins to run from the period of present- ment and acceptance. "Sight draft" and "Sight bill" are bills payable at sight. SIGISMUND, EMPEROR OF GER- MANY AND KING OF HUNGARY AND BOHEMIA, second son of the Emperor Charles IV.; born in 1368. On the death of his father, in 1378, he be- came Margrave of Brandenburg, and was occupied four years in visiting his states, and receiving their homage. He married, in 1385, Maria, daughter of Ludwig Louis, King of Hungary, and was crowned king the same year. He soon after ex- tended his dominions by the conquest of the Wallachia. His queen dying in 1392, his claim to the crown of Hungary was contested by Ladislaus V., King of Po- land, but unsuccessfully; and the fre- quent conspiracies formed against Sigis- mund by the nobles made him suspicious and cruel. Alarmed by the conquests of the Turks, he sought aid of France and England; and a great battle was fought at Nicopolis in 1396, in which the French, under the Count of Nevers, were defeated and almost all slain, the Hungarians fled without fighting, and Sigismund nar- rowly escaped and led a wandering life for 18 months. In 1410 he was chosen emperor by one party of the electors, Jobst, Marquis of Moravia, being chosen by another party, and Wenceslaus, who had been deposed, still retaining the title
