_India-rubber._—Scraps and powder of hard, vulcanized, moulded and cemented by heat and pressure: Charles Morey, January 9. _India-rubber, Vulcanized._—Treated with alkalies and oil to remove sulphur: Sigismund Beer, May 29. _India-rubber._—Crushed, washed, treated with potash, or soda, in vacuum, and washed to purify: A. G. Day, June 10. _India-rubber Sheet._—With surfaces not vulcanized, united to cloth: Nathaniel Hayward, May 6. _India-rubber._—Surface of vulcanized made rough, then coated with cement, and heated to 235° to render adhesive: Nathaniel Hayward, April 15. _India-rubber._—Treatment of sulphured rubber with drying oils; or common rubber with sulphured oils: Wm. F. Shaw, August 12. _India-rubber._—Treatment of vulcanized with nitric acid and fusel oil, to purify and render adhesive: Henry Forstrick, October 28. _India-rubber._—Boiling in potash to remove sulphur from the surface of vulcanized and render adhesive: Richard McMullin, March 18. BOOK V. CHAPTER I. TANNING. The science or art of Tanning is the process by which the animal hide or skin is converted into _leather_, thus rendering it subservient to the use of man. The art of tanning in its most simple form was known to antiquity, and consisted simply in the drying and cleansing the skins, which were then converted into articles of clothing. Thus used, they answered but a temporary purpose, as the re-absorption of moisture would speedily cause them to decay. The Egyptians were among the earliest tanners of whom we have any definite account, and Thebes was justly celebrated for its artificers in leather. But unlike most of the arts in which the Egyptians excelled, they do not seem to have reached an equal degree of skill in the preparation of leather, although it was wrought by them into tapestry, and made to subserve various useful purposes. In later times this useful art has been reduced to scientific principles, owing to the investigations of Sir H. Davy, Sequin Proust, and others. Leather considered chemically is a compound of tannin and gelatine, possessing the qualities of durability, pliability, and insolubility in water. The important elements in the manufacture of leather are, first, _cleansing and softening the skins_. Second, the depilation or removal of the hair. Lime is principally used for the latter purpose, although any agent which possesses the power to soften or destroy the roots of the hair, and facilitate its removal is equally desirable. The process of depilation with lime is slow, and tanners have yet to learn that practically there are other chemical processes which will greatly facilitate it. Hydrosulphuret of calcium is recommended.