S>escrfptfon, Bnalsfs, Specific Gravity of IRubber, &c* 379 



Father Clavijero says that rubber, in Mexican, is called Olliu, or 

 Olli, a word derived from Olquahuitl ; that it is a tree of medium size 

 with a smooth trunk of a yellowish color, having long leaves, white 

 flowers, and a yellow fruit, angular in shape, containing kernels of the 

 size of a nut, white and with a yellowish skin. The kernel has a bitter 

 taste and the fruit always grows close to the bark. He also says that 

 it is a very common tree in Guatemala. 



I have seen a great many rubber-trees in Soconusco and in the 

 western part of Guatemala contiguous to Mexico and near the sea; but 

 they were nearly all small; the large ones had been cut down for 

 reasons which will be mentioned later. There is a great difference 

 between the size and shape of the leaves of the two varieties; both 

 have them silky and of a deep green; the small trees are very straight, 

 without leaves, except in the upper part, these being large, hanging 

 down from a bough like a stem, and the bark is of a light color. 



On the San Carlos farm of Mr. Jeronimo Manchinelli, in the juris- 

 diction of Tuxtla Chico, in the Soconusco district, I saw three trees 

 that the owner had found growing on the place when he took posses- 

 sion of it, thirty-one years ago, and which he thinks cannot be less 

 than thirty-five years old. They are of an enormous size; I measured 

 the trunk of one of them; it was two metres in diameter, and the 

 space shaded by its foliage had a diameter of at least twenty or twenty- 

 five metres ; its branches were also very large, the leaves smaller than 

 those of the smaller trees and their form entirely different from them. 

 Mr. Manchinelli having never extracted any rubber from them, did 

 not know the quantity that each tree could give, but experts calculated 

 that it could not produce less than about fifty pounds a year. 



The trunk of the rubber-tree of Soconusco is of a spongy white 

 wood, with large pores plainly visible to the eye. 



Very little is known regarding the discovery of the rubber- tree. 

 The French astronomers sent to Peru, in 1735, were the first who 

 called attention to it. It was found afterward at Cayenne by Frisman, 

 in 1751. Dr. Priestly refers to it in the preface of his work entitled 

 Prospective, printed in 1770. Various experiments made for utilizing 

 rubber are mentioned in the Memoirs of the Academy of Sciences of 

 France for the year 1768. 



Rubber is extracted by making an incision in the bark of the tree 

 from which flows a liquid very much like sap in color and thickness. 

 Exposed to the sun or the fire, the watery part evaporates and the 

 rubber remains. Exposed to the air, it loses its white color and be- 

 comes dark. 



This liquid is of a light yellow color with a specific gravity of 

 1012. The rubber separated from the sap rises to the surface like 

 coagulated albumen, and when heated with water, its specific gravity 



