224 



DESCRIPTIVE BOTANY. 



it off and knead it into masses, and work it into vessels to hold water and 

 other substances. More than a century after the appearance of Torquemada's 

 work, a scientific description was read before the French Academy by La 

 Condamine, and was published in the transactions of the .Vcademy. (Jublet, in 

 1755, described the hevea botanically. 



At the beginning of the present century the usefulness of the gum had not 

 been developed ; in its native state it was soft and sticky in a high tempera- 

 ture, hard and inelastic wlien exposed to the cold, and hence of very little 

 practical value. In 1842, three liundred and fifty years after it was first seen 

 by Europeans, experiments showed'lt to possess the power of uniting with sul- 

 pliur. When thus combined, it is said to be \Tilcanized ; it is not affected by 

 temperature, and resists solvents. At the will of the manufacturer it may be 

 made very pliable and more elastic than in its natural state, or very hard. 



Preparation. — The mode of- harvesting this remarkable substance is to 

 wound the tree by piercing the bark to the down-flowing sap, which is a 



yellowish-white, milky fluid. This, as it 

 flows out, is caught in vessels of clay or 

 bamboo, and carried to the camp, where 

 it is smeared over an instrument resem- 

 bling a wooden shovel, and held over a 

 smoky fire. When the first smearing is 

 coagulated or hardened, another coat is 

 put on, and the process is repeated until 

 the successive layers have produced a coat- 

 ing of eight inches or more in thickness, 

 when it is slit down the side, slipped off, 

 and hung up to dry and harden. It at 

 first presents a silver-gray color, soon 

 changing to yelloAv, and finally to a dingy 

 black, as seen in commerce. It has been 

 suggested that the vinegar of wood, or 

 pyroligneous acid of the smoky fire, plays 

 an important part in its coagulation, as 

 the gum prepared in this manner is supe- 

 rior to that of any other preparation . 

 The South American gum was formerly 

 hardened upon clay moulds in form of bottles and lasts, and when in a proper 

 state the clay was picked out. 



In India the mode of collecting the sap destroyed the trees. The govern- 

 ment has taken it in hand, and formed plantations, and less destructive modes 

 of harvesting are now practiced. 



Use. — The uses to which India rubber has been applied since the vulcan- 

 izing process has been put into practice are so numerous that only a few can 

 be mentioned here ; in fact it would be difficult to enumerate all the uses to 

 which gum elastic has been put. It enters into the manufacture of every sort 

 of waterproof clothing used for man or beast. The messenger boy encases 

 himself in India rubber, and defies the pelting storm. The soldier in the 

 camp spreads down his rubber blanket, and the cavalryman on the march, in 

 a storm, protects himself and his horse by a covering of gum elastic cloth. 

 It is manufactured into toys for the infant, bands for holding papers and 

 packages together, boots, shoes, hats, beds and cushions, life-belts, garden- 

 hose, door-springs, roller-skates, bumpers for railroad cars, etc. 



Hevea Braziliensis (Caoutchouc). 



