18 Is the Eucalyptus a Fever-destroying Tree ? 



slate-coloured paint. After the copper head has been in use 

 for some time, this paint-like substance dries into scales 

 having a slate-pearly appearance. (Sample on the table.) If 

 the distillation has been by water, and the mother liquor 

 remaining in the still is subjected to a little evaporation, 

 this acid may be detected in the vapour by litmus paper. 

 (Experiment shown.) 



Should the evaporation be carried to farther concentration, 

 the acid aroma becomes palpable around the locality of 

 operation ; persistent, and very refreshing ; in short, there 

 is no expelling this acid out of the gum-resinous extract 

 orming in the pan. The aroma of the acid may be detected 

 in the air along with that of the oil, when travelling in the 

 bush. (A specimen of the strong acid on the table.) 



The special features of this acid as existing in all eucalypts 

 are, that in those species supplying oil most abundantly, the 

 acid is not so prominent as it is in those yielding the 

 medium quantities ; whilst those species which contain oil 

 sparingly, contain also but little of the acid. In like man- 

 ner, this applies to the resin bodies, and these facts are 

 worthy of particular note, as they go to show, first — That 

 those species yielding largely of oil are not so abundant 

 either in resin or acid, and that those of medium oil yield are 

 well charged with both. In proof of this, the amygdalina, 

 our largest oil-producing species, during its active period of 

 supplying the volatile oil, does not throw off much resin ; 

 but when it begins to lodge in the interstices of the bark 

 and wood, and exudes outwardly, the oil is diminished in 

 quantity in the leaves. 



The globulus, or blue gum, yields a continued steady 

 supply of oil and acid throughout the year ; but when the 

 tree is extra resiniferous, the acid is abundant, and the oil 

 small in quantity. 



The rostrata, or red gum, is another illustration. It 

 produces a very small quantity of oil, but the volatile acid is 

 very abundant, so much so that the red gum wood owes its 

 aroma entirely to this acid. 



The sideroxylon, or iron bark, are trees of good dimen- 

 sions, and supply oil abundantly ; but the leaf surface on 

 each tree is small in comparison with other species. Here 

 the resin is so abundant, that its enormous bark is every- 

 where studded with gum resin. 



All these characteristics and others of like nature point to 

 the following conclusion — that the volatile oil is the base of 



