" 
 Gamboge. It contains indeed between 
- four and six per cent. less gum than Siam 
. Gamboge, and between two and four per 
- cent. less than the other specimens of Cey- 
-. Jon Gamboge which I have examined ; but 
— this difference can scarcely be held the less 
to constitute it a true Gamboge.! 
Since 
executing this analysis I have received, 
through the great kindness of Mrs. Colonel 
Walker, another specimen similar to that 
of Dr. Duncan. Although I have not sub- 
mitted it to analysis, from unwillingness to 
spoil the specimen, I am satisfied, from the 
great ease with which it makes an emulsion 
= with water, that this specimen must con- 
tain a full proportion of gum. 
From the whole of the previous account 
of the properties and composition of the 
different kinds of Gamboge, the following 
conclusions may, I think, be reasonably 
drawn 
It has just been shown, that the compo- 2 
sition of this concrete juice varies some- 
what in the respective proportions of its two 
essential ingredients, as it is produced by 
the same plant growing in the same climate 
and country. It is plain, therefore, that a 
difference in the place of growth of the 
may occasion a similar difference, 
greater in degree; and consequently that 
Siam Gamboge may perfectly well be pro- 
duced by the same species which is known 
to produce the Gamboge of Ceylon. 
It further appears, that the proportion 
of gum to the coloured resin may vary 
Somewhat, without the emulsive quality of 
the article being materially altered; but 
that a very small diminution of the gum 
Wa certain proportion will render the 
gum-resin incapable of forming a smooth 
emulsion, which property is indispensable 
= employment as a pigment. 
"e next place, there can be scarcely 
4 oubt, that the Gamboge-tree of Cey- 
: Aad be made to yield, with due care, 
and perfect Gamboge, so far as con- 
! On : 
careful comparison, it appeared that the resin 
ON THE SOURCES AND COMPOSITION OF GAMBOGE. 
243 
cerns the art of painting. And the condi- 
tions for success probably are, 1. That the 
exudation be collected from the tree with 
more care than at present, so as to be kept 
free of woody fibre and the darker parti- 
cles of bark, by which the purity and live- 
liness of the yellow tint are somewhat im- 
paired. 2. That care be taken to ascertain 
in what circumstances of season, soil, cul- 
tivation, or the like, the exuded juice con- 
tains the due proportion of gum, that is, 
not less than 20.5 per cent. of the gum- 
resin when perfectly dry. 3. That where 
the gum is rather deficient, it be supplied 
by express addition. Probably, indeed, 
the whole Gamboge of Ceylon may be im- 
proved by the addition of three or four per 
cent. of gum; and at all events some kinds 
of it require such addition, as seems well 
known to the Cingalese, who, according 
to Mrs. Walker, when they use it as a 
igment, sometimes add a little of the gum 
of the Feronia elephantum, or Wood- 
apple. In regard to the first of these con- 
ditions, it ought to be known, that, accord- 
ing to the only account hitherto obtained 
of the mode of collecting Gamboge in 
Siam, namely, the information communi- 
cated to Koenig by a Portuguese priest, 
who said he had witnessed the process, 
this variety of the drug is actually prepar- 
ed not from the bark, but from the leaves, 
by bending down the branches, cutting the 
leaves across, and collecting the droppings. 
Koenig’s account certainly does not seem 
very probable ; yet it ought to be kept in 
view, and subjected to trial in Ceylon. The 
Cingalese method is to obtain it from the 
bark, sometimes by making incisions 
through it, and sometimes by shaving off 
portions of the outer bark as large as a 
man’s palm. It seems scarcely necessary 
for me to point out how readily this crude 
method will lead to the introduction of 
woody fibre into the article, or how easily 
the method may be improved so as to ex- 
clude such impurity. 
As to the use of Gamboge in medicine, 
I am satisfied that the Ceylon variety pos- 
sesses the properties of the finest Siam 
Gamboge in full perfection. Mrs. Walker 
