432 VEGETABLE SUBSTANCES. 



sure to the sun and air ; it is scraped off from the 

 bark with a knife or chisel. The annual product 

 from one tree rarely exceeds three pounds. Few trees 

 sustain the effects of this continued exhaustion longer 

 than ten or twelve years. 



The purest of the gum, coming first from the tree, 

 is white, soft, and fragrant, and is called head ben- 

 jamin. This resin is moderately hard and brittle; 

 on the application of friction or heat it yields a fragrant 

 odour. It is totally soluble in alcohol, from which, 

 like other resins, it may be precipitated by the addition 

 of water. Its specific gravity is T092. 



Benzoin is much used in perfumery and in fumi- 

 gation, forming a principal ingredient in aromatic 

 pastils. It is imported into England from the East 

 Indies : 7,335 Ibs. were retained for home consump- 

 tion in 1830. It is imported of very different qualities, 

 and classed 1st, 2d, and 3d, and varying in price from 

 5 to J45 per cwt. according to the class whereto it 

 belongs. A duty of 2s. per Ib. is levied on its impor- 

 tation into England. 



Labdanum is another resinous juice used by per- 

 fumers. It is the product of a species of cistus, 

 a well-known and beautiful evergreen shrub, with 

 evanescent flowers, scarcely expanding before their 

 petals drop and are strewed around. The particular 

 species, the juice of which affords labdanum, is the 

 cistus creticus, a native of Candia. Tournefort, in 

 his voyage to the Levant, relates that when the air is 

 dry the resin spontaneously issues out of the pores of 

 the leaves, whence it is carefully collected. The more 

 common way of obtaining it, as pursued by the pea- 

 santry, is to employ a staff with several leather thongs 

 fastened to its end, with which the leaves are gently 

 struck until the juice is thus caused to exude : this 

 adheres to the leather and is scraped off with a knife. 



