158 UTILIZATION OF 3AEK. 



its being impregnated, after it has been tanned, with the essential 

 oil distilled from the outer white bark of the birch. Amongst our 

 numerous species some are sure to be found capable of yielding a 

 similar oil. 



Section II. — Baek fob dyeing. 



Irrespective of tannic acid, which with salts of iron gives various 

 shades of green, purple, maroon, grey, and black, almost all our 

 barks yield, by mere decoction, a large proportion of other colouring 

 matters, some of them red and yellow, but most of them giving some 

 shade of brown. Contrary to tannic acid, most of these colouring 

 matters reside in .the rhytidome, so that the older a tree is, the 

 larger will be the amount of colouring matter present in its bark. 

 It is principally these colouring matters which cause a difference 

 in the colour of leather, according to the species of bark used. 

 Up to the present, scientific dyers have not taken up a study of our 

 various tree-barks, and hence their capabilities as dyeing materials 

 for use on a large scale are still only a matter for the future to 

 reveal. All the dyes are permanent. That these dyes are likely 

 to be greatly fancied the moment they become known seems certain 

 from a casual use of the brown dye obtained in bleaching the fibre 

 of Bauhirda Vahlii. Mr. Wilson, the gentleman who experimented 

 with the fibre in England, employed the colour in dyeing silk, and 

 produced some elegant shades by different reactions. The bark of 

 Acacia arabica, Hardwickia binata, Soymida febrifuga, Terminalia 

 tomentosa, and sal are well known to yield extremely rich browns. 



Section III. — Fibees. 



All woody species yield fibre, but there are only a very few, of 

 which the fibres are strong enough to be twisted without breaking, 

 and the number is still smaller of those the ultimate fibres of which, 

 remaining after the completion of the cleaning and bleaching pro- 

 cesses, are long enougb to be spun. All fibres suitable for cordage 

 and spinning are also excellent for paper-making, for which a great 

 many others also are well adapted. The fibre of the living bark 

 alone is fit for use. The woody species whose bark yields utilizable 

 fibres belong almost exclusively to the Malvaceae (^Hibiscus, Thes- 

 pe8ia,Kydia, Adansonia),^QTTl\3i.CQ?Q {Greioia), the Sterculiacese 

 {Sterculia, Helicteres, Eriolcena), the Urtioacese {Bcehmeria, Pouzol- 

 zia, Sarcochlamys, Maoutia, Debregeasia, Broussonetia, Antiaris, 

 Ficus, Ulmus, Sponia), the Leguminosese {Senbania, Desmodium, 

 Bauhinia, Hardwickia) , and the Asclepiadeae ( Calotropis, Marsdenia, 

 Fergalaria) . Careya arborea and Daphne papyracea are two well- 



