^{page 607 note *} Fig. 120 in the New Edition, just published.

^{page 607 note *} Phil. Trans., 1815, p. 49, 38; and 1816, p. 97.

^{page 608 note *} This method consists in placing a film of selenite (sulphate of lime) between the polariser and the substance to be examined. If the polarising structure is produced by circular crystals, it will appear covered with spots, or minute sectors, of two different colours, the one being a tint a little lower, and the other a tint a little higher, than that of the selenite. The higher tint is the sum of the tints of the two substances, and the lower their difference, the tint of the selenite being increased by that of two of the sectors, and diminished by that of the other two.

^{page 613 note *} Treatise on Light, § 770, Figs. 155, 156, 157, Plate IX.

^{page 614 note *} In making these observations, and on many other occasions, I have felt the great inconvenience of the present, and in general, perhaps the best, arrangement of the compound microscope. High powers being always obtained by object-glasses of short focal length, it is almost impossible, in transparent structures, to develope them, when they consist of lines or parts of different thickness. Vision is destroyed by the refractions and diffractions of the intromitted light. The only remedy for this is to use ½-inch, or even 1 or 2-inch object-glasses, and obtain the power that is required at the eye-piece, by means of grooved and other lenses of diamond, garnet, &c.

^{page 619 note *} Stearine gives the same polarised halos as oil of mace.

^{page 622 note *} Discoveries in the Ruins of Nineveh and Babylon. By Austen H. Layard, M.P. Appendix, p. 674–676.