[38] Smith’s Opticks, vol. ii. p. 388, § 977.
[39] Essay on Single Vision, &c., p. 44.
[40] We may use also the lens prism, which I proposed many years ago in the Edinburgh Philosophical Journal.
[41] [See Chap. i. pp. 33-36].
[42] For 1852, vol. xvii. p. 200.
[43] These solid telescopes may be made achromatic by cementing concave lenses of flint glass upon each end, or of crown glass if they are made of flint glass.
[44] Phil. Mag., Jan. 1852, vol. iii. p. 19.
[45] American Journal of Science, 1852, vol. xv. p. 68.
[46] See my Treatise on Optics, 2d edit., chap. vii. p. 65.
[47] See Cosmos, vol. ii. pp. 622, 624.