—— gun cotton, 314.
—— gutta percha baths, 415.
—— head-rests, 338.
—— hydrosulphite of soda, 74.
—— India-rubber substituted for yellow glass, 71.
—— iodized paper, 48. 92. 140, 141. 187. 293.
—— iodizing difficulty, 605.
—— Le Gray and the collodion process, 47. 389.
—— lens, test for, 485. 533. 555. 582.
—— Lyte's mode of printing, 557.