SAP. 73 



In Guiana the Indians fashion the caoutchouc into the bottles 

 vvhich are so comraon in trade : they make a clay mould, and this 

 they cover by immersing it in the milk freshly drawn from the tree ; 

 they allow it to coagulate, which it does very speedily, especially if 

 it be exposed to the smoke of a wood fire. This first layer being 

 coagulated, they continue the same process until the desired thick- 

 ness is attained. The mould is then broken and taken out piece-meal 

 from the interior of the caoutchouc bottle which has been formed. 



The workmen of Quito, who are very dexterous in manufacturing 

 caoutchouc, make shoes and buskins of it, by applying it in the 

 milky state Over moulds of the proper fashion. They also render 

 tissues impervious by spreading it in the same state between two 

 pieces of stuff or cloth; the interposed milk becomes coagulated, and 

 forms a thin elastic lamina, very preferable to the caoutchouc applied 

 by the aid of solvents. 



The Indians of Choco sometimes procure this substance by felling 

 the tree, and receiving the milk, which then flows in a stream, into 

 large wooden moulds, generally formed from a hollow stem of the 

 guaduas. By keeping the mould open, the milky mass coagulates 

 after some time. Several of these masses of caoutchouc, which 

 were brought to me by the Indians of the Chami nation, were but 

 slightly elastic ; their color also was extremely deep. It is probable, 

 that by proceeding in this way, the milky juice is mixed with large 

 quantities of the internal sap which is much less milky. 



Several trees in the valley of the Magdalena which bear the name 

 of caoutchouc, which, however, are neither the hoevea, nor the ja- 

 tropha, also yield a coagulable juice, which may be confounded with 

 the elastic gum ; it is, I believe, caoutchouc combined with a large 

 quantity of wax, and probably also of resin ; this caoutchouc pos- 

 sesses but little elasticity. 



M. Faraday found in the milk of the hoevea, in 100 parts : 



Water 56 



Caoutchouc 32 



Bitter azotized matter soluble in water and alcohol 7 



A substance soluble in water and alcohol (sugar) 3 



100 



As this milk will remain fluid for a considerable time, provided it 

 t)e protected from the air, advantage Kas been taken of this property 

 to convey it to Europe. It is sent in well-filled, hermetically-sealed 

 bottles. 



GUMMY AND RESINOUS SAPS. 



I place under this head the saps of those trees which yield gum 

 from incisions in their trunk, as the acacia vera and acacia Arabica, 

 which grow in Arabia, and from which gum-arabic is obtained ; 

 acacia Senegal, which also furnishes a species of gum. In general, 

 in very warm countries, the mimosas produce gummy matters in 

 abundance. 



The elaborated sap of the coniferae and terebinthaceaj consists 

 jhiefly of resinous matter, dissolved in an essential oil composed of 



7 



