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than if they ugg boots canada<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> the non-corresponding halves of the binocular eye form a monocular eye. Experiment will show this to be the case. Hence stereoscopic images falling both of them in the temporal, or both of them in the nasal halves of the binocular eye, will appear precisely as if one of them fell in the nasal and the other in the temporal half of the monocular eye, or as if both fell upon separate points in any one half of the monocular eye. Thus the images in the temporal halves a, b,and d,/, can no more combine than if they ugg boots canada were a, b,and d, e.Hence a, b, d, e, are monocularly disparate; so also d, c, a, b.Now, since monocular combination of disparate images never takes place, we can demonstrate that it can never take place in stereoscopic combination; at least, where the figures to be combined are such as Wheatstones original illustration represented: namely, two lines which <a href="http://www.jindantuan.com/"><strong>男士靴*</strong></a> indicate opposite inclinations to the median plane. This is shown in the following lines, where Aand B,the upper ends of the lines, will fall upon temporal halves of the retina when Cand Dfall upon the fovea, <a href="http://www.jindantuan.com/"><strong>ugg雪地靴 </strong></a> and yet fusion is as apparent as if it were real. The lower ends fall upon the nasal halves, and fusion is also apparent; the total resultant being a line with the upper end nearer the observer than the lower, and apparently upright or at an inclination to the plane of the paper. But it is effected by non-corresponding halves of the eye.To illustrate this, take Fig. , Rand Lrepresenting the two eyes. Let/ and Brepresent two figures farther from the median line .fiV-than Cand D. Aand Bmay represent the upper ends of the lines in Fig. , and Cand Dthe centres; both together forminga plane geometrical outline for a stereoscopic figure such as Wheatstone employed. Take Efor the point of fixation before combination, so that we may suppose A, B,C, and Dto lie in the horopter. cand care the fovea centrales;and when the eyes are fixated for an object at E,its two images will fall, one upon cand the other upon c;while those of Awill fall upon eand e,of Bupon aand a,of Cupon dand d,and of cheap uggs for sale Dupon band Now, a and a, band b, cand c, dand d, eand S,being corresponding points, the several objects will be seen single while they are in the horopter; but the position of their images upon the retina must be noticed before indicating the effect of stereosoopic cheap uggs uk combination. The images of each object fall upon corresponding halves of the retina; but the images of Aand Bcompared, also of C and Dcompared, fall upon non-corresponding halves of the retina. Now, in stereoscopic combination the object is to make Aand B,or C and D,appear to coincide respectively; that is, appear upon the fovea. This may be done by converging or by diverging the eyes. But this can be effected only by fusing one image of Aor C in the one eye with the image of <a href="http://www.jindantuan.com/"><strong>雪地靴怎么清洗 </strong></a> Bor Drespectively in the non-corresponding half of the other eye. By convergence the fusion will be of images at present in the temporal halves; by divergence, of images in the nasal halves: that is, by the former combination, must be of extrafoveal, and by the latter of intra-foveal, images, aand b,and dand e,are extra-foveal, because they lie in the temporal halves: dand t,and aand b,are intra-foveal, because they lie in the nasal halves of the eyes. Now, if we converge the eyes so as to bring the image of Cand Dinto the fovea, it is evident that the combination takes place only by what are extra- foveal images when the point of fixation is E.Convergence to produce combination of C and Drequires a new point of fixation in the median line at the intersection of the lines which represent the course of light from C to d,and from Dto b.When this is effected, the fovea? cand care shifted, the former to band the latter to d,to receive the images at those points. But thus, while the images of Cand Dare fused in thefovea, those of Aand Bstill fall upon extra-foveal points as far from the new position of cand cas ais from b,and / from a. But being both extra-foveal, they fall in temporal and therefore <a href="http://inbookmark.com/mybookmark.php"><strong>qq团* </strong></a> non-corresponding halves of the retina.
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