That is very doubtful, because tannin, thus artificially prepared, must probably always be more expensive than that which is obtained from bark. But the fact is extremely curious, as it affords one of those very rare instances of chemistry being able to imitate the proximate principles of organised bodies. The last of the vegetable materials is _woody fibre_; it is the hardest part of plants. The chief source from which this substance is derived is wood, but it is also contained, more or less, in every solid part of that plant. It forms a kind of skeleton of the part to which it belongs, and retains its shape after all the other materials have disappeared. It consists chiefly of carbon, united with a small proportion of salts, and the other constituents common to all vegetables. EMILY. It is of woody fibre, then, that the common charcoal is made? MRS. B. Yes. Charcoal, as you may recollect, is obtained from wood, by the separation of all its evaporable parts. Before we take leave of the vegetable materials, it will be proper, at least, to enumerate the several vegetable acids which we either have had, or may have occasion to mention. I believe I formerly told you that their basis, or radical, was uniformly composed of hydrogen and carbon, and that their difference consisted only in the various proportions of oxygen which they contained. The following are the names of the vegetable acids: The _Mucous Acid_, obtained from gum or mucilage; _Suberic_ - - - from cork; _Camphoric_ - - - from camphor; _Benzoic_ - - - from balsams; _Gallic_ - - - from galls, bark, &c. _Malic_ - - - from ripe fruits; _Citric_ - - - from lemon juice; _Oxalic_ - - - from sorrel; _Succinic_ - - - from amber; _Tartarous_ - - - from tartrit of potash: _Acetic_ - - - from vinegar. They are all decomposable by heat, soluble in water, and turn vegetable blue colours red. The _succinic_, the _tartarous_, and the _acetous acids_, are the products of the decomposition of vegetables; we shall, therefore, reserve their examination for a future period. The _oxalic acid_, distilled from sorrel, is the highest term of vegetable acidification; for, if more oxygen be added to it, it loses its vegetable nature, and is resolved into carbonic acid and water; therefore, though all the other acids may be converted into the oxalic by an addition of oxygen, the oxalic itself is not susceptible of a further degree of oxygenation; nor can it be made, by any chemical processes, to return to a state of lower acidification. To conclude this subject, I have only to add a few words on the _gallic acid_. . . . . CAROLINE. Is not this the same acid before mentioned, which forms ink, by precipitating sulphat of iron from its solution? MRS. B.