VEGETABLE SUBSTANCES. 



Copal is one of the hardest of resins, but easily 

 reducible to a fine powder ; this union of hardness 

 with colourless transparency makes it highly valuable 

 as a varnish for pictures, white-wood works, and for 

 a variety of other purposes, among 1 others for snuff- 

 boxes, tea-trays, and similar articles of domestic use 

 or ornament. 



Mr. Sheldrake has discovered that camphor has a 

 powerful action on copal ; pulverized and triturated 

 with a small portion of camphor, it softens and be- 

 comes a coherent mass. Alcohol and oil of turpentine 

 are both made solvents of copal by the addition of 

 camphor, which is thus an essential auxiliary in the 

 formation of copal varnishes. 



Copal is brought to us principally from Africa ; a 

 very small quantity coming occasionally from the East 

 Indies and South America. It is admitted into this 

 country at the same rate of duty as animi ; its price 

 being from Is. 3d. to 3s. per lb., according to its 

 quality and description. The quantity retained for 

 home consumption in 1830 was 22,893 Ibs. 



The beautiful black varnish of Japan, which the 

 artists of Europe have in vain sought to equal, is a 

 resinous juice exuding from incisions made in the 

 trunks of certain trees. One of these trees is that 

 whose fruit is sometimes brought into Europe as a 

 medicinal drug, the Semecarpus anacardium. It 

 grows wild in China as well as Japan, but improves 

 by cultivation, and affords three times more of this 

 valuable product than when in a wild state. The 

 resin is extracted by incisions made in the bark in 

 spring, and when the juice, which is received in shells, 

 does not flow readily, several hog's bristles moistened 

 with water are introduced into the wound, causing it 

 to run anew. When the tree is somewhat exhausted, 



