THE CAOUTCHOUC GROUP. 261 



lacquer, for tooth-powders and washes. la medicine it is 

 used for its astringent property. 



232. The resin called Botany Bay Gum, or Grass- 

 tree Ghim, covers the stems of several Australian species of 

 Xanthorrhaa, of the Lily family {Liiiaeece). The red resin 

 is from X. auslralii; it has a color very similar to that of 

 Dragon's-blood. It is very lustrous, and the streak is 

 orange. The yellow resin (called also Black Bay Gum) is 

 X. hastilis. It is, when fresh, yellowish to brownish ; when 

 old it has a crust of a deep brown color. This gum has 

 its origin in a metamorphosis of tissue, and is very complex 

 in chemical composition. It is used for coloring alcoholic 

 varnishes, and especially for varnishes for metalic objects. 



THE CAOUTCHOUC GROUP. 



233. In the Caoutchouc Group are included Caout- 

 chouc, Gutta-Percha, and Balata Gum. These occur, in 

 the form of granules, in the milky juice of many plants 

 belonging to the orders Euphorbiaceoe, Apoeynacece, Asclepi- 

 adaeecB, SapotaceoB, Compositoe, Lobeliacece, and Artocarpaeeos. 

 Some fresh juice sent in sealed vessels from South America 

 to Faraday, and by him analyzed, showed the following 

 composition : 



Caoutchouc 31.70 per cent. 



Wax, etc 7.13 per cent. 



Gum ? (soluble in water) 2.90 per cent. 



Soluble Albuminoids 1.90 per cent. 



Water, Acetic Acid, and Salts .... 56.37 per cent. 



I. Caoutchouc was used by the Indians of Brazil and 

 Guiana from remote times, in the manufacture of vessels, 

 shoes, etc. The natives of East India likewise used it, from 

 time immemorial, for lining baskets for holding liquids, for 

 torches, etc. Caoutchouc, from South America, was first 



