[48] Id. vol. vii. p. 494.
[49] Id. vol. iii. p. 658.
[50] Phil. Trans., 1852, p. 7.
[51] Mr. Wheatstone’s paper was published before I had pointed out the deformities produced by large lenses. See p. 130.
[52] The Eye in Health and Disease, by Alfred Smee, 2d edit. 1854, pp. 85-95.
[53] This expression has a different meaning in perspective. We understand it to mean here the point of the sitter or object, which is to be the centre of the picture.
[54] Cosmos, Feb. 29, 1856, vol. viii. p. 202.
[55] It is only in a horizontal direction that we can see 180° of the hemisphere. We would require a circle of eyes 2½ inches distant to see a complete hemisphere.
[56] See Chapters [X]. and [XI].
[57] When any external light falls upon the eye, its picture is reflected back from the metallic surface of the Daguerreotype, and a negative picture of the part of the Daguerreotype opposite each eye is mixed with the positive picture of the same part.