ITS TOBMATIOV 359 



ay an etiolated caoutchouc. The humidity of the soil seema 

 to* account for the undulating form of the edges of the 

 dapicho, and its division into layers. 



I often observed in Peru, that on pouring slowly the 

 milky juice of the hevea, or the sap of the carica, into a 

 large quantity of water, the coagulum forms undulating 

 outlines. The dapicho is certainly not peculiar to the 

 forest that extends from Javita to Pimichin, although that 

 is the only spot where it has hitherto been found. I have 

 no doubt, that on digging in French Guiana beneath the 

 roots and the old trunks of the hevea, those enormous 

 masses of corky caoutchc'ic,* which I have just described, 

 would from time to time be found. As it is observed in 

 Europe, that at the fall of the leaf the sap is conveyed 

 towards the root, it would be curious to examine whether, 

 within the tropics, the milky juices of the urticese, the 

 euphorbiacea3, and the apocyneae, descend also at certain 

 seasons. Notwithstanding a great equality of temperature, 

 the trees of the torrid zone follow a cycle of vegetation ; 

 they undergo changes periodically returning. The existence 

 of the dapicho is more interesting to physiology than to 

 vegetable chemistry. A yellowish-white caoutchouc is now 

 to be found in the shops, which may be easily distinguished 

 from the dapicho, because it is neither dry like cork, nor 

 friable, but extremely elastic, glossy, and soapy. I lately saw 

 considerable quantities of it in London. This caoutchouc, 

 white, and greasy to the touch, is prepared in the East 

 Indies. It exhales that animal and fetid smell which I 

 have attributed in another place to a mixture of cascuiu 

 and albumen.f When we reflect on the immense variety 



* Thus, at five or six inches depth, between the roots of the Hymene 

 rourbaril, masses of the resin antme (erroneously called copal) are dis- 

 covered, and are sometimes mistaken for amber in inland places. This 

 phenomenon seems to throw some light on the origin of those large masses 

 of amber which are picked up from time to time on the coast of Prussia. 



f- The pellicles deposited by the milk of heavea, in contact with the 

 atmospheric oxygen, become brown on exposure to the sun. If the 

 dapicho grow black as it is softened before the fire, it is owing to a slight 

 combustion, to a change in the proportion of its elements I aw 

 surprised that some chemists consider the black caoutchouc of com mem 

 as being mixed with soot, blackened by the smoke to which it has beep 

 exacted. 



