From Paper Mill to Pressroom

sited upon a wire cloth by the passage of a volume of water in which they have been suspended. The pulpy film thus formed becomes a sheet of paper, after the expulsion and evaporation of the water which served as a medium for their deposit. The minute fibers composing this hypothetical sheet of paper may have been isolated from one of several sources of raw materials in present commercial use, or the sheet may be composed of a mixture of different fibers, all more or less pure cellulose, in accordance with the preliminary treatment each has undergone. The principal sources from which American paper fibers are derived are cotton and linen rags, hemp, jute, wood, straw; and waste papers. Previous to the year 1840, the sources were limited to rags. These are almost wholly composed of pure cellulose fibers, which give up their non-cellulose concomitants with slight resistance. The more severe chemical treatments necessary for the isolation of cellulose fibers, from wood, for example, half of which is non-cellulose in structure, were unknown to early paper-makers, and only became possible after the discovery of bleaching-powder by Tennant, and the manufacture of soda by Le Blanc. Although experiments in search of suitable substitutes for rags began to be made in the eighteenth century, it wasKeller's invention of ground wood in 1840, Routledge's work on esparto grass and wood with a soda process in 1854, and our own fellow countryman Tilghmann's patent of t...