^{page 111 note *} Traité de Mineralogie, tom., i., p. 512, 521.

^{page 111 note †} Philosophical Transactions, 1818, p. 424.

^{page 111 note ‡} Treatise on Light, art. 1076.

^{page 111 note §} See Report of the Eighth Meeting, and Trans. of Sections, p. 10–12.

^{page 111 note ∥} I shewed this experiment in 1836, at Lacock Abbey, to Mr Fox Talbot, and several members of the British Association. At the meeting of the British Association at Manchester, in 1842, a friend handed to me, in the sectional meeting, a “solution of stramonium in ether,” which dispersed a bright green light. I described the phenomenon to the meeting, and it is noticed in the Transactions of the Sections, p. 14. Upon making the solution myself, I cannot obtain the same tints, either from the stalk or the dried leaves of the plant. The solution of the leaves disperses a brilliant red tint, like that mentioned in the text. The solution put into my hands must, therefore, have been one of the seeds of stramonium, or of some other substance possessing internal dispersion in a high degree.

^{page 113 note *} Philosophical Transactions, 1845, p. 143.

^{page 114 note *} The best method of seeing this experiment, is to take the solution into the open air, where the whole light of a blue sky can fall upon its surface. I have in this way seen the blue line perfectly luminous at that stage of a December twilight when there was not light enough to read by. I consider, therefore, the light of the sky as peculiarly susceptible of this species of dispersion.

^{page 115 note *} In one of these experiments a piece of green fluor, from Alston Moor, when immersed in the quiniferous solution, dispersed a fine violet blue light, at the distance of three-fourths of an inch from its surface. In another experiment, a beam of light that had been dispersed in the solution of quinine, again suffered dispersion at two inches distance from the surface of a piece of Derbyshire fluor.

A beam of light that has passed through the Esculine solution disperses blue light, but not copiously, when transmitted through the quinine solution; but the beam that has passed through quinine is copiously dispersed when transmitted through Esculine.

^{page 118 note *} In the alcoholic solution of Esculine, the faint-blue approaches to violet. The polarisation is like that in quinine.

^{page 120 note *} In the experiment with Prussian blue, which is a very splendid one, the particles are mechanically suspended in the water; so that we have here an ocular demonstration that the particles are the cause of the dispersion and the quaquaversus polarisation.