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 STEREOTYPE that they appear to have in the stereoscopic illusion in the instrument; also, the axes of the eyes are inclined to each other in the same manner when looking in the stereoscope as they would be if they regarded the above men- tioned group of solid objects. Hence the eye is affected exactly as when it views these real objects, and a stereoscopic perception is the effect. Indeed, a simple rule for all illusions of sight, as Helmholtz concisely states, is " that we always believe that we see such objects as would, under conditions of normal vision, pro- duce the retinal image of which we are actual- ly conscious." The reason that a stereoscopic perception is obtained when we look at a near object is due to the fact that the impressions produced by the two different pictures of this object on the retina, and the muscular adjust- ment of the ocular axes so that they converge to the same point of the object, are translated, through the experience of touch, as effects be- longing to solidity. Some have imagined that they had explained stereoscopic perception by the fact that the axes of the eyes converge to point after point on the object in rapid succes- sion, and thus, as it were, triangulate the posi- tions of these points by a series of visual tri- angles, which have for their base the distance separating the yellow spots, or macula lutew, on the retinas of the eyes (see EYE, fig. 1), and for sides the lines drawn from these spots to the various observed points of the object. But Dove showed that the stereoscopic perception is obtained when we illuminate the pictures in the stereoscope by the flash of a Leyden jar ; and Prof. Rood has shown that the dura- tion of this illumination is only four billionths of a second, a duration altogether too short to allow the eyes time to make any motion. Others have maintained that a combination of the impressions produced upon both retinas takes place, and thus the two plane retinal pic- tures are fused into a stereoscopic perception ; but the retinal impressions do not combine, for Dove has shown that when dull black is alone viewed with one eye, while white is regard- ed with the other, the perception produced is similar to that of the metallic surface of gra- phite ; whereas the real combined sensation of these impressions is a dull gray. From these and many other experiments we learn that " two distinct sensations are transmitted from the two eyes, and reach the consciousness at the same time and without coalescing ; that accordingly the combination of these two sen- sations into the single picture of the external world of which we are conscious in ordinary vision is not produced by any anatomical mech- anism of sensation, but by a mental act." See "The Stereoscope," by Sir David Brewster (London, 1856), and "Recent Progress of the Theory of Vision," by Helmholtz, published in his "Popular Lectures on Scientific Sub- jects " (New York, 1874). STEREOTYPE. See PEINTING, vol. xiii., p. 850. STERLING 377 STERLING. See POUND STERLING. STERLING, a city of Whitesides co., Illinois, on the N. bank of Rock river, and on the Chicago and Northwestern and the Rockford, Rock Island, and St. Louis railroads, at the terminus of the Rock River branch of the Chicago, Burlington, and Quincy line, 110 m. W. of Chicago and 28 m. E. of the Mississippi river; pop. in 1860, 2,428; in 1870, 3,998; in 1876, 5,312. It is lighted with gas, and is supplied with water by the Holly system of works and by an artesian well 1,650 ft. deep, discharging 700 barrels an hour. It is chiefly devoted to manufacturing. The river at this point is spanned by a dam of solid masonry, 1,100 ft. long and 7 ft. high, which with the 9 ft. natural fall of the rapids above affords an immense water power. The value of the manufactures of Sterling and Rock Falls (op- posite) in 1874 was about $4,250,000, and the number of hands employed upward of 1,000. The articles are principally of wood, includ- ing agricultural implements, school furniture, feed mills, pumps, burial cases, carriages and wagons, building materials, butter tubs, wash- ing machines, barrels, hedge trimmers, tables, mittens, machinery, mineral paint, paper, &c. There are five flour mills, a distillery (the lar- gest in the United States), two tanneries, and a pork-packing establishment. Sterling has a national bank, three public school houses, two reading rooms, a public library, two weekly newspapers, and 12 churches. It was laid out in 1836, and incorporated as a city in 1857. STERLING, John, a British author, born at Kames castle, isle of Bute, July 20, 1806, died at Ventnor, isle of Wight, Sept. 18, 1844. He was educated at Glasgow and Cambridge uni- versities, in 1827 went to London, and for a few months in 1828 edited with F. D. Maurice the "Athenaeum." In 1830-'31 he passed 15 months on St. Vincent island, "West Indies, for his health, the state of which required inter- vals of residence in the south of France, Ma- deira, and Italy through the rest of his life. In 1834 he took deacon's orders and became curate to his former college tutor J. C. Hare, rector of Hurstmonceaux, Sussex ; but in Feb- ruary, 1835, he went to London to devote him- self to literature. In August, 1838, he found- ed the Anonymous club, afterward called the Sterling club. Among the members were Car- lyle, Tennyson, Moncton Milnes, John Stuart Mill, J. 0. Hare, C. L. Eastlake, Sir Edmund Head, and G. C. Lewis. Sterling published "Arthur Coningsby," a novel (London, 1833) ; "Minor Poems" (1839); "The Election," a poem (1841) ; and " Strafford," a drama (1843). After his death appeared "Essays and Tales,^' collected from various reviews, with a memoir by J. C. Hare (2 vols. 8vo, 1848); "Life of John Sterling," by Thomas Carlyle (1851) ; " Twelve Letters by John Sterling," edited by W. Coningham (1851) ; and " The Onyx Ring," from "Blackwood," with a biographical pre- face by Charles Hale (Boston, 1856).