In the Royal Institution Journal already noticed, we find several communications from him, under the titles of "Observations on different methods of obtaining Gallic Acid;"--"On the processes of Tanning," &c. All the new facts however, discovered in the course of his experiments, were embodied in a long and elaborate memoir, which was read before the Royal Society on the 24th of February 1803, and published in the Philosophical Transactions for that year. It was entitled "An Account of some Experiments and Observations on the constituent parts of certain astringent Vegetables, and on their operation in Tanning. By Humphry Davy, Professor of Chemistry in the Royal Institution. Communicated by the Right Honourable Sir Joseph Banks, P. R. S." Although Seguin and Proust had already examined many of the properties of that vegetable principle to which the name of _tannin_ had been given, yet its affinities had been but little examined; and the manner in which its action upon animal matters may be modified by combination with other substances, had been still less considered. His principal design in this enquiry was to elucidate the practical part of the art of tanning skins, so as to form leather; but in pursuing this object, he was necessarily led into chemical investigations connected with the analysis of the various bodies containing the tanning principle, and the peculiar properties and value of each. The vegetable principles that had been regarded as more usually present in astringent infusions, are _tannin_, _gallic acid_, and _extractive matter_. In attempting to ascertain the relative proportions of _tannin_ contained in different infusions, Davy was led, after various trials, to prefer the generally received method of precipitating by means of _gelatine_ procured from isinglass. In using this test, however, he discovered that several precautions were necessary;--that the solution should be quite fresh,--that it should be as much saturated as may be compatible with its fluidity,--and that the precipitate obtained should be reduced to a uniform degree of dryness. It is evident that if the quantity of gelatine in the solution, employed as the precipitant, be known, it will only be necessary to ascertain the weight of the precipitate produced by it, in order to learn the absolute proportion of tannin present in any specimen.