ADVANTAGES OF HEATING THE OPEN AIR. 
What is necessary is, a production of heat, in the air itseli, 
throughout all heights of the vegetation ; and the production of 
this is the problem to be solved,—a problem which is either pos¬ 
sible, or not possible, although a good deal ot management would 
be required. I can see no impossible element in it. 
In a future communication, I may, perhaps, if this should find 
favour in your estimation, and that of your readers, point out my 
notion of the finest effect which could be given to this out-door 
heating, but in the mean time I confine myself to the simple problem 
of its practicability. From what I have observed and heard, I am 
inclined to think that Mr. Weeks, junior, of Gloucester Place, 
King’s Road, Chelsea, is the horticultural artist, in whose hands 
the project would be most likely to succeed ; and the modus ope- 
randi would be that combination of hot-water tubes, and pipes for 
heated air, which answers so well for keeping up the temperature 
of frames in winter, and for the ripening of cucumbers and other 
productions that grow near the surface. Any requisite degree of 
temperature may be given to the hot water which circulates in the 
tubes, and they may be raised to the required height; and if 
the air pipes open by trumpet* mouths below, and smaller aper¬ 
tures above, being water-tight both at the entrance and at the 
exit, the air within the tubes might, according to their lengths, be 
raised to the degree of heat required, which in the case of plants 
merely hardy would not require to be much above the freezing 
point. The heat radiating from the hot-water tubes, and the 
directly heated air, would both contribute to dry the atmosphere, 
and by this means adapt it for the intended purpose. 
In this there appears to be no difficulty, as it is merely turning 
upon edges that same apparatus which lies flat when applied to 
the heating of a pit or frame. To this heating with water and 
air, various additions might be made, which would contribute to 
its general effect. For instance, the grounds might be sheltered 
from the chilling winds, by copses of planting, and the throwing 
up of embankments, or slopes, facing that direction in which the 
rays are hottest. Canopies might be erected over tropical plants, 
to protect them from the cold, and to confine the heat when ra¬ 
diated from the earth during the coldest time of the night; and 
by a judicious blending of these contrivances with others which 
would readily suggest themselves to an ingenious artist, the 
- temperature of the air might be kept above the freezing point, 
