jExpirimenti on Caout-c^ouc, or Indian Ruiiar. 439. 



k equally fo in Cajeput oil, an efletjtial oil,, fijid to be obtained from the leaves of Me- 

 laleuca Leucadendron, Both foluijpns appear perfc^, tjjjck, ^nd very glutinous. 

 Spirits of wine, added to the folution m Cajepiit oil, foon wnited with the oil, and left 

 the caout-ehoue floating on the mixture in a foft femi-fluid ftati% which, on being 

 wafhed in the fame liquor, and expofed to the air, became as firm as before it was dif- 

 folved, and retsined its elaftic powers perfeftly, while ip the intermediate ftates be- 

 tween femi-fluid and firm, if could be drawn out into long, tranfparent threads, refem- 

 bling, in the polifli of their furface, the fibres of the tendons of animals ; when they- 

 broke, the elaftipity was fo great, that each end inftantaneoudy returned to its refpec- 

 tive mafs, Through all thefe ftages the le^fl. preffure with the finger and thumb united, 

 different portions, as perfeftly as it they never had been feparated, and without any 

 clammlnefs, or flicking to the fingers, which renders moll of the foUuions of caout- 

 chouc, fo very unfit for the purpofes for which they are required. A piece of catgut 

 covered with the half infpiflated folution, and rolled between two fmooth furfaces, 

 foon acquired a polifli, and confiftence very proper for bougies. Cajeput oil, I alfa 

 found a good menftruum for American caoutrchouc, which was as readily feperated by 

 the addition of a little fpirit of wine, or rum, as the other, and appears equally fit for 

 ufe, as I covered a piece of catgut with the wafhed folution, as perfeftly as with that of 

 Urceola. The only difTerence I could obferve, was a little more adhefivejaefs from hjt 

 aot drying fo quickly; the oil of turpentine had greater attraftion for the C30ut-ehouc 

 than for the fpirits of wine, confequently remajjied obftinately united to the former, 

 which prevented its being brought into that Hate of firmnefs fit for handling, which it 

 acquired when Cajeput oil was the menftruum. 



The Cajeput folution employed as a varniih did not dry, but remained moift and 

 clammy, whereas the turpentine folution dried pretty fall. 



Expreffed oil of olives and linfeed proved imperfeft menftruvTOs while cold, as the 

 eaout-chouc, in feveral days, ■ was only rendered foft, and the oils yifcjd, but with a 

 degree of heat equal to that which melts tin, continued for about twenty-five minutes- 

 it was perfeftly diflblvcd, but the folution remained thin and void of elafticity. I alfo 

 found it foluble in wax, and in butter in the fame degree of heat, but ftill thefe folu- 

 ♦ibns were without elafticity, or any appearance of being ufeful. 



I fhall now conclude what I have to offer on the caout-chouc, or Urceola elaftica, 

 with obferving that fome philofophers of eminence have entertained doubts of the Anae. 

 rican caout-chouc being a fimple vegetable fubftance, and fufpeft it to be an artificial 

 produftion, an idea which I hope the above detailed experiments will help to eradicate, 

 and confequently to reftore the hiftories of that fubflance by M. De la Condamine and 

 •thers, to that degree of credit to which they feem juftly enthled, in fupport of which 

 k may be fmther ojjferved, that befidcs Urceola elaftica there are many other trees, 



3 L 2 natives 



