TAN manufaSured from those of calves, dogs, &c. They are washed in water; then plunged in lime- water, and deprived of their hair by the same operation as hides ; after removing all uneven and su- perfluous matters, the skins are soaked in a pit of water impreg- nated with the dung of pigeons, for a week or ten days, in order to ex- traft all the particles of lime, grease, &c. Next, they are treat- ed in a similar manner with the hides; and, in the coin-se of five or six months, they will be suffici- ently tanned. — The leather thus prepared, is now conveyed to the currier ; and, after undergoing the process detailed, vol. ii. p. 110, it is used for the upper parts of boots, shoes, &c. Such are the old methods com- monly practised in tanning : these, however, being too tedious and ex- pensive, various expedients have lately been devised, with a view to shorten the respedive processes, and to procure substitutes for oak- bark. Thus, Dr. Macbride pro- posed the use of vitriolic acid, in- stead of that obtained from vege- tables ; which, having been found very serviceable for distending the pores of the skins intetided for lutts, has been generally adopted by tanners; as it improves the lea- ther in point of durability ; and at the same time tends to facilitate or simplify the operations. He also recommended lime-water to be substituted for die common fluid, to promote the extra ftion of the astringent matter from the oak- bark ; but, the former being very powerful, and apt to injure the tex- ture of the leather, it is seldom employed. Oak-leaves, gall-nuts, dried and TAN [187 pulverized heath, the barks of the birch and willow- trees, the dried and powdered leavfts of the wild laurel, and numerous other vege- table produi3:ions, have been tried, and proposed, as useful substitutes for oak-bark : numerous experi- ments were also made with plant^ by Gleditscit, Bautsch, Boh- MKK, and other writers ; but, as wn state the results of these in tie pro- gress' of our work, it remains only to mention the following patents, among the multitude granted at du'Ferent periods ; namely : 1. The privilege obtained by Mr. Sa- muel AsHTON, in January, 1794, for his new method of tanning.-— 2. Mr. John Tucker's patent, date • in May, 1795, for a mode of tanning and making leather in a much shorter period, and of a su- perior quality, than can be effefted by the common method. — 3. Mr. William Desmokd's, in January, 179O ; for a process communicated to him (by M. Segoin), of tan- ning hides, &c. by rendering them more solid and incorruptible in water.— 4. Mr. Robeut Cross's, in April, 1797, for a tan pit on a new construction, and a method of tanning in one-half of the usual time, &c. — 5. Mr. Francis Brew- ing's, in June, I799, for an im- proved processof tanning hides and skins, — As the specification of these patents, however interesting to the tanner, are partly too diffuse, and partly ot such nature as not to ad- mit of abridgment, the curious re.ader will consult the 1st, 3d, 6th, and 1 1 til vols, of the Repertory of Arts, &c. where full specifications are inserted/ and occasionally il- lustrated with plates, — See also CuKRYiNG, Hides, Leather, Skins, &c. ' Tait-
