80 
BRITISH FERNS. 
that both the root and the young fronds are accounted 
good food in Japan. 
The ashes of ferns in general, and of this fern in 
particular, contain a large quantity of potash, and, on 
this account, are of much value to the glass manufac- 
turer, soap boiler, and to all washerwomen ; it is also 
used extensively on the Continent, in the preparation of 
kid and chamois -leather. 
There is a kind of varnish used in the manufacture of 
china, called fern-oil. The Chinese obtain it thus : — they 
take a very great quantity of well-dried fern, and spread 
it thickly over a piece of ground, upon this they place a 
layer of large limestones, newly calcined ; on these they 
sprinkle just enough water to wet the surface. Upon 
the stones they lay another thick bed of fern, and then 
place another layer of limestone, which they moisten, 
covering it as they did the last with quantities of dried 
fern. They build on thus, with alternate tiers of fern # 
and lime, till the heap is ten feet high. Then they set 
fire to the fern, which soon burns away and leaves a 
quantity of mixed lime and ashes. This mixture is laid 
between new beds of fern and burnt again, and the 
operation is repeated five or six times. When the last 
burning is concluded, the mixture of lime and ashes is 
carefully collected, and thrown into large vessels of 
water, one pound of Rekio being added to every hundred- 
weight of it, and the whole stirred together ; the finer 
part then floats on the surface like cream, while the 
coarse falls to the bottom : this thev take off, and leave 
to stand alone, when, after a time, the creamy part sinks 
and the water is then poured off. The residuum is the 
fern- oil. This oil they mix with oil of stone, procured 
in a similar manner, and with the mixture they cover all 
