638 ORD. XXXIX. Tricocca@.  sipHonra ELASTICA. 
pear-shaped bottles, which are said to be formed by spreading the 
juice of the Siphonia over a proper mould of clay, and as soon as 
one layer is dry another is added till the bottle be of the thickness 
desired. It is then exposed to a dense smoke, or to a fire, until 
it becomes so dry as not to stick to the fingers, when by means of 
certain instruments of iron or wood it is ornamented on the outside ° 
with various figures. This being done it remains only to pick 
out the mould, which is easily effected, on being first anne 
with water. 
The substance, thus manufactured, is so well known as to render 
any particular description of it unnecessary. It may be subjected 
to the action of some of the most powerful menstrua without 
suffering the least change, while its pliability and elasticity are 
eminently peculiar to itself. It is true that the lactescent juice 
of several vegetables may be converted into a substance resembling 
the Caoutchouc, but no art has yet been discovered to give it the 
same properties. 
The Chinese elastic resin is said to be prepared of castor oil and 
lime;' or, according to Retzius, it is nothing but a certain ex- 
pressed oil evaporated by heat:* hence its easy solubility. — 
With a view to investigate the interesting nature of the Caout- 
chouc, and to render it of more ‘general utility, several able 
chemists have been diligently employed, especially Macquer,* 
Achard,' Juliaans,* and Berniard,’ from whom its chemical history 
is to be learned: our duty however is to state only some of the 
principal facts. 
Though it appears that neither water nor alcohol, aided by all 
the heat capable of being produced in Papin’s digester, could 
dissolve this substance, yet its solution was effected not only by 
t V. Faujas de Saint-Fond Suite de la description des experiences aérostatiques 
tom. 2. p. 258. 
& Pharm. reg. veg. p.60. * Mem. de l’ Acad. des Sc. de Paris, pour 1768. 
‘1! Chymisch phys. Schriften cap, De resina elastica. 
* Diss, de Resina elastica Cayennensi. +} See Rozier Obs. sur la Physique. tom. 17. 
