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XVI. eien upon a Subitande called Dapéche from South 
i America, By William Allen, Esq. F.L.S. 
Read May 1, 1805. 
Tur worthy. Yi ice-president. ef this Society, T onas Pader, 
Esq. favoured me with a specimen of a substance sent to Sir 
Joseph Banks from South America, by Humboldt. It is said to 
be found at the depth of two or three feet from the surface of 
the earth. In appearance it very much resembles a dried Fun- 
gus, having the same spongy texture : internally it is nearly 
white; and although in its external character so different from 
Caoutchouc, the results of a variety of experiments leave no 
Toom doubt. that itisa modification of the samé substance. 
The milky j juice of. the Hawea Caoutchouc and Jatropha elastica, 
-from which the Caoutchouc or common Indian rubber i is ob- 
tained, undergoes a considerable change on ‘exposure to atmo- 
spheric air; like blood recently drawn from the veins, it separates 
into two parts, viz. an aqueous fluid, and the concrete substance 
called Elastic Gum. 
The specimen appears to. have been produced by successive 
deposits of milky juice; but on account of its peculiar situation, 
the changes have probably not taken place in the same order, nor - 
to the same extent, as when completely exposed to the powerful 
agency of atmospheric air. 
The Dapéche burns freely when held to the cándle; it removes 
black-lead marks with the same Bici as Caouteligue: ; and in 
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