EUCALYPTUS TREES. 59 
bucketful of wood-ash, such as we daily remove from 
our domestic fire-places, contains about twenty-five 
pounds, from which, accordingly, about two and one 
half pounds of inferior, or one and one fourth pounds 
of superior potash, may be obtained; the former 
being worth about sixpence per pound, the latter 
double the price. For ascertaining the contents of 
carbonate of potassa in crude potash or pearlash, cer- 
tain instruments, well known as alkali-meters, are 
constructed. The heaviest ashes, as a rule, contain 
the greatest proportion of potash. The brake-fern, so 
common on many river-banks and sandy tracts of the 
country, is rich in this alkali. 
Apart from my subject, I may, however, say that 
there are other sources of potash-salts than trees alone. 
Chloride of potassium is obtained from some large 
salt-beds, for instance, in Prussia. From this source it 
was supplied to British manufactories, in 1869, to the 
extent of one hundred and fifty-four thousand four 
hundred and sixty-eight hundred weight, valued at 
above £60,000. This chloride is besides obtained, under 
Mons. Balard’s process (Report of Juries at the Inter- 
national Exhibition for 1862), in considerable quanti- 
ties from sea-water, as one of the contents to be util- 
ized. From this chloride the various potash salts, 
otherwise largely obtained from pearlash, can be also 
prepared. Chlorides and sulphates, if they occur in 
crude potash, can, in the process of purification, almost 
completely be removed through crystallization from 
the greatly concentrated solution. 
Let us now approach another forest industry, one 
quite unique and peculiar to Australia—namely, the 
distillation of volatile oil from Eucalyptus and allied 
