212 ON THE TANNING MATERIALS AND 



discontirmed in Tuscany, where formerly it was much esteemed. That 

 which is at present used is prepared at Lyons and Huddersfield ; and 

 the suggestions of Giobert and Cantu have not yet succeeded in inducing 

 our workmen to use the colouring lichens, which are plentiful in Sar- 

 dinia and the Alps. The samower (Carlhamus tinctorius) is used for 

 dyeing skins and giving to them a metallic lustre. Ascoli, in the 

 Marches, and Castrocaro, in Tuscany, have some commerce in this 

 article. 



Sorgho (Sorghum glycicliilum) is also a colouring plant, the stem 

 and the rind ol w T hich, being fermented, produce a crimson, yellow, and 

 red dye. Under the name of " violet woods," I have grouped a 

 certain number of dyewoods, belonging to different species, but which 

 all alike have the property of giving a colourless substance, susceptible 

 of being converted into a crimson red colouring matter by the influence 

 of acids, heat, and light ; each of these agents will give wood, or its ex- 

 tract, or any textile fabric, passed through a decoction of the wood 

 itself, different tints varying from purple to violet, and from green to 

 brown. Arnotto (Bixa orellana), in non-alkaline solution is used to give 

 the leather particular tints. 



Besides the Tsai, and the leaves of the Chica (Bignonia Chica'), with 

 which the Indians of South America prepare the curare, or curaruru, we 

 have also to mention the numerous series of dyeing substances — red, 

 violet, and bordering upon violet, known in commerce under the im- 

 proper names of fuchsines, azuleines, &c, produced by the action of 

 bichlorate of tin and mercury, arsenic acid, and the peroxide of man- 

 ganese upon aniline, extracted from the distillation of coal-tar. These 

 colours are brilliant, but not durable ; they resemble the yellow colour 

 of berberry — in that they are more durable on tanned leather, the pre- 

 sence of the tannin, and the chemical substance of leather having some 

 influence upon these phenomena. 



As regards the process undergone by the skins in their conversion 

 into leather, tanning by steeping has been generally relinquished, but 

 is still used for goats' and sheep's skin. The processes followed by 

 tanners, and the substances which they make use of, vary very much in 

 each province, and, indeed, in every place. It cannot be said that there 

 exists an Italian method of tanning ; that which bears this name in Tus- 

 cany, and which is confined to that province and to a few other locali- 

 ties, being itself doomed to disappear for economical reasons. 



Italian, or rather Tuscan tanning, consists essentially in giving the 

 skins a preparatory treatment (a ddobbo) by immersion in six or seven 

 successive baths (ripassature) of a decoction of myrtle leaves, to which 

 are added oak bark and valonia : the next thing done is the covering 

 over (raminorto), which is effected by spreading the skins in a pit, with 

 layers of a composition made of ground valonia, steeped in a decoction 

 of myrtle. The tanning lasts from 300 days to a year, according to the 

 thickness of the skin. The small streaks, more or less regular, which 



