54 FOREST CULTURE AND 
At last, with mild heat and final constant stirring, 
the whole is evaporated to dryness. This dry mass 
represents crude potash more or less impure, accord- 
ing to the nature of the wood employed. 
A final heating in rough furnaces is needed, to ex- 
pel sulphur combinations, water, and empyreumatic 
substances; also, to decompose coloring principles. 
Thus pearlash is obtained. 
Pure carbonate of potassa in crude potash varies 
from forty to eighty per cent. Experiments, as far 
as they were instituted in my laboratory, have given 
the following approximate result with respect to the 
contents of potash in some of our most common trees. 
The wood of our She-oaks (Casuarina suberosa and 
Casuarina quadrivalvis), as well as that of the Black 
or Silver Wattle (Acaciadecurrens), is somewhat rich- 
er than wood of the British Oak, but far richer than 
the ordinary Pine woods. 
The stems of the Victorian Blue Gum-tree (Euca- 
lyptus globulus), and the so-called swamp Tea- tree 
(Melaleuca ericifolia), yield about as much Potash as 
European Beech. 
The foliage of the Blue Gum-tree proved particu- 
larly rich in this alkali; and as it is heavy and easily 
collected at the saw-mills, it might be turned there to 
auxiliary profitable account, and, indeed, in many 
other spots of the ranges. 
A ton of the fresh leaves and branches yielded, in 
two analyses, four and three quarters pounds of pure 
potash, equal to about double the quantity of the av- 
erage kinds of pearlash. The three species of Euca- 
lypts spontaneously occurring close around Melbourne 
—the Red Gum-tree (Eucalyptus rostrata) ; the Man- 
