230 SOURCES OF TANNIN. CAOUTCHOUC. 



Japonica (Japanese earth, from its earthy appearance), which is 

 much valued in medicine from its astringent properties, and 

 which acts very powerfully on gelatin. It is a dry extract, pre- 

 pared by boiling the heart-wood of the tree, cut into chips, and 

 then evaporating the superfluous water. The Mangrove tree, of 

 the East and West Indies, is another from which a large quan- 

 tity of tanning matter may be obtained. This curious tree 

 grows on the borders of the sea and on the banks of rivers; its 

 stem is supported by a large number of branching roots, which 

 rise out of the water in arches several feet high, closely inter- 

 twining with each other ; and the branches hang down, and send 

 forth similar roots, as in the Banyan (. 152). The extract made 

 from its bark is used for tanning in many parts of the West Indies 

 and in Hindostan ; and it is said to perform its office more per- 

 fectly in six weeks, than oak-bark does in ten, producing a leather 

 more firm and durable. In New Holland, there is an abundance 

 of a species of Acacia, which is cut down for the purpose of 

 clearing land ; and from this it has been ascertained that an 

 extract may be made, fully equal to oak-bark. As, notwith- 

 standing the distance of the colony, it can be supplied very 

 cheaply, so long as there is a superfluity of the Acacias it will 

 probably take the place in great degree of oak-bark. The Euca- 

 lypti of New Holland also contain a large quantity of tannin in 

 their bark. 



367. Another secretion of great importance in the arts, and 

 of which new and valuable applications are constantly being dis- 

 covered, is Caoutchouc, commonly known as Indian Rubber. It 

 was first brought as a great curiosity from South America about 

 150 years ago ; and for a long time nothing was known of the 

 source from which it was obtained ; nor was it applied to any 

 useful purposes, except the rubbing-out of pencil marks, from 

 which it took its name. It is known to be contained abundantly 

 in the juices of many trees, growing in tropical climates ; as well 

 as, in smaller quantity, in many plants of temperate regions : it 

 seems to form an essential part of the milky juices (as they are 

 termed, from their white colour, rather than from their pro- 

 perties), which are characteristic of several tribes of Vegetables, 



