. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. B to C D, the accommodation required helps us inour decision, and if we know the height of the table, the angle underwhich the lines A B and C D are seen beneath the horizontal plane,in which the eye lies, assists in determining our opinion as to thedistance. The same table, placed at double the distance from theeye, gives another perspective image, in which a b : c d = 2 : 3(compare Fig. 83 I), and in which the angles at a, b, c and ddeviate less from the right angles (II). We, h
. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. B to C D, the accommodation required helps us inour decision, and if we know the height of the table, the angle underwhich the lines A B and C D are seen beneath the horizontal plane,in which the eye lies, assists in determining our opinion as to thedistance. The same table, placed at double the distance from theeye, gives another perspective image, in which a b : c d = 2 : 3(compare Fig. 83 I), and in which the angles at a, b, c and ddeviate less from the right angles (II). We, however, consider thedimensions to be equally great, and the angles to be right angles,only because such is usually the case with tables, and we inferthat the length of the table amounts to about half the distance fromCD to the eye. If there be now only some object, whose truemagnitude or distance is known, this serves as a standard whenceto judge of all other objects, whose relative magnitude and DETERMINATION OF DISTANCE. 157 distance are inferred upon the same principle (the perspectiveprojection). Fie.
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Keywords: ., bookcentury1800, bookdecade1860, bookidonanomalieso, bookyear1864
