Waste paper, bookbinders' shavings, etc., can be used for making the paper. As much wool as possible should be employed, because the wool fiber has a greater resistance than vegetable fiber to the effects of the temperature. By wool fiber is understood the horny substance resembling hair, with the difference that the former has no marrowy tissue. The covering pellicle of the wool fiber consists of flat, mostly elongated leaves, with more or less corners, lying over each other like scales, which makes the surface of the fiber rough; this condition, together with the inclination of curling, renders it capable of felting readily. Pure wool consists of a horny substance, containing both nitrogen and sulphur, and dissolves in a potash solution. In a clean condition, the wool contains from 0.3 to 0.5 per cent. of ash. It is very hygroscopical, and under ordinary circumstances it contains from 13 to 16 per cent. humidity, in dry air from 7 to 11 per cent., which can be entirely expelled at a temperature of from 226 to 230 degrees Fahrenheit. Wool when ignited does not burn with a bright flame, as vegetable fiber does, but consumes with a feeble smouldering glow, soon extinguishes, spreading a disagreeable pungent vapor, as of burning horn. By placing a test tube with a solution of five parts caustic potash in 100 parts water, a mixture of vegetable fibers and wool fibers, the latter dissolve if the fluid is brought to boiling above an alcohol flame, while the cotton and linen fibers remain intact.