In this argument Mr. Griffin ignores the fact that esparto grass is a crop which gives a yield of cellulose practically equal to wood, and of equal, if not superior, quality. Although it is not available for American mills, it is worth citing in contradiction to the flat statement that “there is no substitute for wood.” Furthermore, there is no evidence that the American crops furnish an inferior fiber, though the cellulose yield is less. It is quite possible that the low cellulose yield may be compensated for through the production of by-products along with the paper-making material. Hitherto, however, this low yield and other considerations, as expense of harvesting and packing, have been the factors which have retarded their development, but the increasing scarcity of wood, and its consequent advance in cost, is hastening the day when crop plants will become not only valuable, but necessary adjuncts to the paper industry. [Illustration: RAGROOM, PIONEER MILL, CRANE & CO. The two girls in the foreground are sorting shirt cuttings. Those beyond are cutting them into suitable sizes preparatory to boiling.] CHAPTER FOUR THE CONSTITUENTS OF PAPER The technique of paper-making varies greatly in accordance with each particular product. In fact, so wide is the range of paper products, that the different branches of paper-making severally require knowledge so special that an artisan in one branch might be as useless in another as if it were an entirely different industry. The coating of paper, for example, is an absolutely different trade from that of paper-making. This remarkable diversification is entirely the development of a century, and principally the evolution of the past forty years consequent to the discovery of wood cellulose. To-day the products of the paper-mill are no longer confined to the use of pen or press. We ride on car wheels made in part of paper; sit in paper-seated chairs; drink from paper cups; eat from paper plates; use paper napkins; wrap our food in parchment paper; sheath our buildings with paper without, and wall paper or wall board within; keep out the rain with roofing paper if we please. Our shoes, even, contain a paper part, said to be more durable than leather. Millions of packages, mailing-tubes and boxes are made of paper. It is even spun into a kind of yarn and woven into imitation cloth, while a surprising imitation silk necktie is produced from wood-pulp. In electrical engineering, paper as an insulator is almost indispensable. All these paper commodities, and more, too numerous to mention, require special machinery and treatment. To give an exhaustive treatment of the subject would require volumes, but for the purpose of this book we are principally concerned with printing and writing papers. [Illustration: BOILER ROOM, CRANE & CO. The contents of the rotary boiler have been emptied upon the floor. The next step is to wash and bleach.]