. Human physiology (Volume 1) . es ob-jects, with their variousdegrees of apparent dimi-nution on account of distance, and of foreshortening on account ofobliquity of position, is called perspective. 2. The intensity of light, shade, and colour. —It has beenshown, that the intensity of light diminishes rapidly, according tothe distance of the body, from which it emanates; so that it is onlyone-fourth as powerful when doubly distant, one-sixteenth whenquadruply distant, and so on. This fact is early recognised ; andthe mind avails itself of it to judge, with much accuracv, of rela-tive distance
. Human physiology (Volume 1) . es ob-jects, with their variousdegrees of apparent dimi-nution on account of distance, and of foreshortening on account ofobliquity of position, is called perspective. 2. The intensity of light, shade, and colour. —It has beenshown, that the intensity of light diminishes rapidly, according tothe distance of the body, from which it emanates; so that it is onlyone-fourth as powerful when doubly distant, one-sixteenth whenquadruply distant, and so on. This fact is early recognised ; andthe mind avails itself of it to judge, with much accuracv, of rela-tive distances. It is, however, a pregnant source of optical a bright sunshine, the mountains appear much nearer to ns thanwhen seen through the haze of our Indian summer* In a row a A delightful season, in the southern and western parts of North America moreespecially, generally occurring in October or November; and having nothing similarto it, so far as we are aware, in any other part of the globe. It is dependent upon some. 250 SKNSE OF SIGHT of lamps along a street, if one be more luminous than the rest, itwill seem to be the nearest; and, in the night, we incur thestrangest errors, in judging of the distance of any luminous sky appears nearer to the earth directly above, than it doestowards the horizon ; because the light from above having to passonly through the atmosphere, is but slightly obstructed, whilst aportion only of that, which has to pass through the dense hetero-geneous air, near the surface of the earth, arrives at the eye. Theupper part of the sky being, therefore, more luminous, seemsnearer; and, in the same manner, we explain, in part, why thesun and moon appear larger at rising and setting. The shade of bodies keeps pace with their intensity of light;and accordingly, the shadows of objects near us, are strongly de-fined ; — whilst in the distance they become confused, and the lightaltogether so faint, that the eye at last sees an extent of dis
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectphysiology, bookyear1
