INTRODUCTION. 
XVll 
water to settle at the bottom of the jar ; plant a fern in 
the earth, and then cover the jar with its glass lid, first 
supplying a slip of wash-leather round the rim of the jar, 
which will pretty nearly cut off the communication between 
the internal and external air ; no farther attention will be 
required : the fern will live, thrive, and probably seed, the 
seed also vegetating, and at last the jar will become too 
small for its contents ; no watering is needed ; the moisture 
in the earth will exhale, condense on the glass, trickle down 
its sides, and so return to the earth whence it arose. 
There is no limit to the application of this principle : 
instead of a jar, it is easy to construct in the window-sill 
a box, extending throughout its entire length, the bottom 
and sides being lined with zinc, to prevent the moisture 
from damaging the adjoining wood-work ; then let the 
window be a double one, like those in Russia, leaving a 
space of six or twelve inches between the inner and outer 
glass. The ferns so planted in the box, which should 
contain a depth of five or six inches of light sandy earth, 
will soon fill up the space between the two windows, supply- 
ing the most beautiful curtain or blind that could possibly 
be invented. The plants need not be ferns exclusively ; 
roses, fuchsias, &c., would also thrive ; but it must always 
be borne in mind, that plants requiring a humid atmosphere 
should not be inclosed with those which prefer aridity : of 
course the upper sash alone must be made moveable. 
Extending the plan still farther, a large conservatory may 
be constructed, or even a large garden, entirely inclosed 
with glass ; all the doors should be fitted with great nicety 
h 
