"The bark of certain trees must be procured, so if you can find either oak, hemlock, birch or beech trees, we can probably make a tanning compound which will serve our purpose."
"In what way will the bark of those trees tan the leather?"
"All the barks named contain what is called tannic acid. Other elements also are used, such as gallic acid, alum, sulphate of iron, and copper, salt, and other agents."
"What are the chemicals for?"
Fig. 13. Tanning Vat.
"The tannic acid or the chemicals act on the skins, or, rather on the gelatin, glutin and albumen in the skins, and thus harden the texture and preserve it. Where tannin is not used and only the chemicals are employed, it is called 'tawing' the leather, instead of 'tanning.'"