VISION 237 VIT image is situated, the necessary accom- modation teaches us that it is situated beween the eye and the lens. The effort of accommodation appropriate to each distance is the same whether the rays have actually come from the apparent distant point or not, so long as they ap- proach at a certain angle of divergence; hence rays from clouds reflected in still, turbid water, and continuing their diver- gence after reflection, approach the eye, and are dealt with by it, as if they had proceeded from a great depth below the surface of the water. Similarly the ap- parent depth of objects under water is diminished because the amount of diver- gence of the rays is altered by refrac- tion; and the apparent distance of an object is increased by repeated reflection because after such repeated reflection the rays originally diverging from the object reach the eye diverging as if they had come from a more distant point, the virtual apex of the incomplete cone of ultimately reflected rays. The axis of the double cone of rays, first divergent as it approaches the eye, and then convergent upon the retina within the eye, fixes the direction of the apparent position of the point (which may or may not be the real position, ac- cording to circumstances), and the strain to which the eye is subjected in accom- modation measures the apparent distance in that direction. On ordinary optical principles a point above the direct line of vision comes to a focus at a point of the retina below its center, and vice versa. If the retina could be looked at by another person it would be found that an image of the object is formed on the retina, and that this image is inverted. It has been much questioned how this inverted image can produce the sensation of direct vision. We may observe in the first place that the question is somewhat nugatory, since the individual never becomes directly aware of the inversion or, it may be, even of the existence of the physical image in his own retina; and secondly, that the individual has come strongly to associate, by experience, the top of an object with the act of looking up in or- der to see it, and vice versa. Any in- crease in the magnitude of the retinal image is generally associated with ap- proach of the object, and in the excep- tional cases in which this result can be brought about by means of lenses, even where the real distance is increased, the object seems to approach; this seeming to approach being the result of an un- conscious process of reasoning. The mind, on the basis of tactile experience, interprets any given object as being of Cyc 16 a known or ascertained size; if it comes to look larger, it is inferred that it has come nearer. VISTULA, the largest river that flows into the Baltic; rises in the former Aus- trian Silesia on the N. slopes of the Bieskiden, and is formed by the union of the Black, the White, and the Little Vistulas (Biala, Molinka and Czorna). It flows N. to the village of Vistula, where it forms a waterfall 190 feet in height, then through a rocky valley to the town of Schwarzwasser, where it leaves the mountain land. Before the World War it separated Prussian Silesia from Aus- trian Silesia and Galicia, and after re- ceiving the Przemza flows N. E., pass- ing Cracow, and separating Galicia from Poland as far as Sandomir, where it re- ceives the San, and turns N. N. W., then W., across the great plain of Poland, passing Warsaw, Nowo Georgiewsk, and Plock, and receiving the Pilica and Bug. Near Thorn it entered Prussia, and con- tinues a N. W. course till it receives the Brahe below Broniberg, where it turns sharply N. N. E. At Montau, near Ma- rienwerder, it divides into two branches, the smaller of which, called the Nogat, discharges into the Frisches Haff, while the larger or W. branch after flowing 40 miles farther, again divides at Fiir- stenwerder into two branches, the small- er or E. falling into the Frisches Haff, and the main hranch turning W. and falling into the Baltic at Weichselmiinde, 3 miles N. of Danzig. The total length of the Vistula is 630 miles. As a re- sult of the World War the Vistula has become a river of Poland, flov/ing through Polish territory throughout its entire length, with the exception of about the last 50 miles, which flow partly through East Prussia and partly through territory belonging to Danzig. VIT, VINCEN-ZO DE, an Italian Latinist; born in Padua, Italy, in 1811. He was an ecclesiastic by profession, was a canon of Rovigo, and town librarian, when in 1850 he joined the brotherhood of Rosmini. On his jubilee in 1888 Leo XIII. sent him a gold medal. He edited Forcellini's "Complete Latin Lexicon" in six volumes, and wrote a supplemental seventh volume, giving in 1,000 pages in double columns all the words in recently discovered inscriptions or codices. His minor writings on history, archaeology, and philology have been collected in a uniform edition published at Milan and Florence. His greatest original work is the "Onomasticon," or "Namebook," con- taining all proper names down to the 5th century. Thirty-six years' labor had just brought him to the end of O, clos- Vol. X
