290 Mr Thomas Oxley on Gutta Percha. 



the presentdate. amounts to 6918 piculs,to obtain\vhich69,180 

 trees must have been sacrificed. How much better would it 

 therefore be to adopt the method of tapping the tree prac- 

 tised by the Burmese in obtaining the caoutchouc from the 

 Ficus ektslica (viz., to make oblique incisions in the bark, 

 placing bamboos to receive the sap which runs out freely), 

 than to kill the goose in the manner they ai'e at present doing. 

 True, they would not at first get so much from a single tree, 

 but the ultimate gain would be incalculable, particularly as 

 the tree seems to be one of .slow growth, by no means so 

 rapid as ihcFicus elaslica. I should not be surprised, if the 

 demand increase.?, and the present method of extermination 

 be persisted in, to find a sudden cessation of the supply. 



Properties of the Gutta, 



This substance when fresh and pure is, as already men- 

 tioned, of a dirty white colour, and of a greasy feel, with a 

 peculiar leathery smell. It is not atFected by boiling alcohol, 

 but dissolves readily in boiling sj.irits of turpentine, also in 

 naphtha and coal-tar. A good cement for luting bottles and 

 other purposes, is formed by boiling together equal parts of 

 gutta, coal-tar, and resin. I am indeb'tcd for this hint to Mr 

 Little, surgeon, and tlie above were his proportions. I have, 

 however, found it necessary to put two parts of the gutta, 

 that is one-half instead of one-third, to enable the cement to 

 stand the heat of this climate. When required for use, it 

 can always be made plastic by putting the pot containing it 

 over the fire for a fcAV minutes. The gutta itself is highly 

 inflammable, a strip cut oft' takes light, and burns with a 

 bi'ight flame, emitting sparks, and di'opping a black residuum 

 in the manner of sealing-wax, which in its combustion it very 

 mucli resembles. But the great pecidiarity of this substance, 

 and that which mr kes it so eminently useful for many pur- 

 poses, is the efiect of boiling water upon it. When immersed 

 for a few minutes in Mater above 150° Fahi-enheit, it becomes 

 soft and plastic, so as to be capable of being moulded to any 

 required shape or form, which it retains upon cooling. If a 

 strip of it be cut ofl^, and plunged into boiling water, it con- 

 tracts in size both in length and breadth. This is a very 



