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which I have since been told the finest varieties of Gamboge 
are not quite exempt. To this testimony may be annexed 
that of Mrs. Walker herself, who is a skilful colourist, and 
who both states in her communication to Dr. Graham, that 
she finds Ceylon Gamboge quite equal to that of Siam, and 
has since added, in a very interesting letter to myself, that 
all the additions sometimes made to it by the Cingalese artists, 
such as lime-juice, the gum of the Feronia elephantum, or 
lime-powder, are not only unnecessary, but have likewise 
appeared to her even to injure its tint. 
" The inference, that good Ceylon Gamboge may be easily 
put to use in the art of painting, is borne out by its chemical 
composition. As in the instance of Cake Gamboge, so here, sul- 
phuric ether and cold water do not effect a complete solution, 
but leave about five per cent, of insoluble matter. This, however, 
does not contain any fecula; and it appears to be entirely 
composed of the fibre of the wood and bark introduced acci- 
dentally. It presents visible fibres; is insoluble in all simple 
solvents either hot or cold; burns almost entirely away with a 
good deal of flame and a smell of burning wood, and has a 
dark brownish-black colour. The ashes of this residuum, 
amounting to three per cent, of it, consists of carbonate of lime, 
with a trace of oxide of iron. The following results were 
obtained from three analyses of Mrs. Colonel Walker's speci- 
mens, evidently different in purity. The quantity used was 
100 grains: — 
First. Second. Third. 
Resin, heated at 400°, . •. . 68.8 71.5 72.9 
Arabin, dried at 240°, . . . 20.7 18.8 19.4 
Fibre of wood and bark at 212°, . 6.8 5.7 4.3 
Moisture, 4.6 not ascertained. 
Total 100.9 96.0 96.6 
Moisture not reckoned. 
Here it is evident that the proportion of gum and resin to one 
