TANKING SUBSTANCES. 495 



middling size tree, common in Bengal and the mountainous parts 

 of India, is used by. the natives for tanning. English tanners, 

 however, object to its use on account of the color which it com- 

 municates to the leather. 



The barks of the Mora excelsa, Benth ; Courida (Avicenna 

 nutida), cashew (Anicardium occidentale) , guava and hog-plum 

 (Spondius, lutea, Linn.), have all been successfully used for tanning 

 in Demerara and the "West India Islands, where they are very 

 abundant. Specimens were sent from British Guiana. 



The root of the Palmetto palm (Chcemcerops Palmetto) is 

 stated to be valuable for the purposes of tanning. The leaves of 

 Nerium Oleander contain tannic acid. The bark of a species of 

 Malphigia is much used by the Brazilians. 



The panke (Gunnera scabra) is a fine plant, growing in Chili, 

 on the sandstone cliffs, which somewhat resembles the rhubarb on 

 a gigantic scale. The inhabitants eat the stalks, which are sub- 

 acid, tan leather with the roots, and also prepare a black dye from 

 them. The leaf is nearly circular, but deeply indented on its 

 margin. Mr. Darwin measured one which was nearly eight feet 

 in diameter, and therefore no less than twenty-four in circum- 

 ference. The stalk is rather more than a yard high, and each plant 

 sends out four or five of these enormous leaves, presenting to- 

 gether a very noble appearance. 



The barks replete with the tanning principle should be stripped 

 with hatchets and bills from the trunk and branches of trees in 

 spring, when their sap flows most freely. The average quantity of 

 oak bark obtained from our forests is estimated at 150,000 tons 

 annually, of which Ireland and Scotland furnish but a very small 

 quantity. 



The following table, given by Dr. Ure, shows the quantity of 

 extractive matter and tannin yielded by different substances : 



In 480 parts In 100 parts 



by Davy. by Cadet. 



Sicilian sumach 78 



Malaga ditto 79 



Souchong tea 48 



Green tea 41 



Bombay catechu 261 



Bengal ditto 231 



Nutgalls 127 46 



Bark of pomegranate 32 



Virginian sumach. . . 10 



,, Carolina ditto 5 



Catechu and Gambier are very valuable for tanning, and are 

 alluded to under the heads GAMBIER and ARECA PALM. 



CATECHT: is obtained from the Acacia Catechu, an arboreous tree 

 growing from fifteen to twenty feet high, with a brown and 

 scabrous bark. The interior wood is brown, dark red or blackish, 

 and the exterior white, one or two inches thick. It inhabits various 



