GENERA EUCALYPTUS AND MELALEUCA. 29 



summary statement ; but the manufacturer on the large scale will find 

 that under like conditions the quantity he obtains may often exceed the 

 yield as stated, but will very rarely fall below it. 



The averages appended have been furnished solely for practical pur- 

 poses ; those belonging to the Eucalypti have been derived from the 

 most common and important trees of that genus. In the case of the 

 tea-tree oils the yield has been omitted, in consequence of the great 

 disparity which the species of that genus manifest in this respect, and 

 from the fact that the species ericifolia exists in much greater profusion, 

 and covers larger tracts of country than all the others taken together. 



To enable a comparison to be made between the productiveness of 

 Victorian plants supplying essential oils, and those of other countries, 

 which are frequently dried before subjecting them to distillation, the 

 following determinations of the loss in weight by drying Eucalyptus 

 leaves in the shade have been made, and may be depended upon for 

 their accuracy : — 



E. amygdalina (Dandenong peppermint) loses 50 per cent. 

 E. globulus (blue gum) .... 50 „ 



E. viminalis (manna gum) . . .41 ,, 



E. rostrata.(red gum) . . .58 „ 



Average loss by drying in the shade . 50 per cent. 



The photometric values of the flames produced by the combustion 

 of these indigenous products have been obtained by comparing them 

 with a kerosene lamp with a flat wick -f inch wide, and burning 31 8 

 grains per hour of kerosene of the best quality imported from America. 



It is evident that such of the oils as give a yellow or yellowish light 

 may be made perfect in colour by a judicious admixture with others, 

 giving a purer flame, or by an alteration in the form of the lamp, and 

 that consume! under such modified circumstances they would also emit 

 a greater amount of light. 



Eegarding the suitability of these substances for illuminating pur- 

 poses there can be no question, as they are possessed of all the valuable 

 properties required for the economic production of artificial light. In 

 efficiency and safety they equal the best kerosene, their odour being at 

 the same time more agreeable, while unlike it they leave no stain upon 

 paper or clothing. Endowed with so many advantages, their general 

 adoption in place of lamp oil, kerosene, naphtha, and camphine, will 

 depend solely upon the cost of their production ; and without venturing 

 to express a decided opinion upon a question of such difficulty, the suc- 

 cessful solution of which defends upon an intimate knowledge of local 

 circumstances, the jurors offer the following data, in addition to the 

 information already given, with the view of enabling those who desire 

 to pursue this subject further, to make the calculation of cost for 

 themselves. 



