118 



Selections. 



[No. 7, NEW SERIES. 



in the trunk of the tree at about 30 inches from the ground, on 

 which a fire is lighted and kept up until the incision is charred : 

 soon after this, the liquid begins to flow. It is conducted by a 

 little trough into a vessel placed to receive it. The average pro- 

 duce of one of the better trees in a single season is 30 gallons. 

 Roxburgh (from whom this account is taken*) adds that wood-oil is 

 also produced by Dipterocarpus incanus, D. alatus and D. costatus. 

 The first of these three is reputed to yield the best sort, and in 

 the greatest quantity. 



The wood oil which forms the subject of Mr. Hanbury's notice 

 has been imported in large quantity from Moulmein in Burmah. 

 When filtered, it is a transparent liquid of a somewhat dark brown 

 color when seen by transmitted light, but appearing opaque and of 

 an obscure green if viewed by reflected light. It possesses therefore, 

 in a very marked degree, the dichroisrn observable in all resin-oils 

 obtained by the action of fire. I particularly notice this character 

 which determines the nature of wood-oil, and shows that it is not 

 simply a natural product like Copaiba ; but that it is in part the 

 result of a liquid modification of the Dipterocarpus resin, effected 

 by the agency of heat. This Moulmein wood-oil is of somewhat 

 greater consistence than olive oil; it has a sp. gr. of 964, and pos- 

 sesses an odour and taste very analogous to those of Copaiba. It 

 dissolves in twice its weight of absolute alcohol, with the exception 

 of a minute residue which is deposited upon repose. 



But the most curious property of this oil, already recognized by 

 Mr. Lowe, and afresh observed by Mr. Hanbury, is that of solidi- 

 fying when heated in a closed vial to 266° Fah. ; at this tempera- 

 ture the oil becomes turbid and so gelatinous, that it is not dis- 

 placed upon the inversion of the vial. After cooling, the solidifi- 

 cation is yet more perfect ; but a gentle warmth, assisted by slight 

 agitation, restore its former liquidity. Mr. Lowe has given the 

 temperature of 230° Fah. for the solidification of the oil : I sup- 

 pose that the different temperatures noted by these two observers, 

 may be accounted for by some difference in the liquids on which 

 they operated ; for as the sorts of Copaiba furnished by different 



* flora Indica Vol. ii. 613. 



