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SELECTED ARTICLES. 
not submitted 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 fol- 
lowing conclusions may, I think, be reasonably drawn. 
" It has just been shown, that the composition of this con- 
crete juice varies somewhat 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 tree 
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 co- 
loured resin may vary somewhat, without the emulsive quality 
of the article being materially altered; but that a very small 
diminution of the gum below a certain proportion will render 
the gum resin incapable of forming a smooth emulsion, 
which property is indispensable for its employment as a 
pigment. 
" In the next place, there can be scarcely any doubt, that 
the Gamboge tree of Ceylon may be made to yield, with due 
care, a fine and perfect Gamboge, so far as concerns the art 
of painting. And the conditions 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 particles of bark, by which the purity and liveli- 
ness of the yellow tint are somewhat impaired. 2. That care 
be taken to ascertain in what circumstances of season, soil, 
cultivation, or the like, the exuded juice contains 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 improved by 
