J 34 
GENERAL MANAGEMENT OF GREENHOUSES. 
a little over the grate, gives a proper direction to the current of air rising through 
the fire. This arrangement being completed, a fire is made on the grate, the flame 
is covered with fuel, and the mouth well closed ; the plane and the arch are thus 
converted into a retort. The heat of the fire and of the hot air rising through it, 
which is strongly reverberated from the arch, promotes the distillation of the nearer 
portions of the fuel : the vapours or gases as they rise are whirled into the current 
towards the flue, and meeting with the rush of heated air through the fire are 
inflamed and completely consumed. This process continues till the coal is perfectly 
caked. When a supply is required, fresh coal is placed in the feeder, and thrust on 
by the screw and box, which thus pushes forward the coke on the plane, till it falls 
on the grate, and then serves to distil and cake the new quantity. 
The command of heat is much greater, with less trouble, and the annoyance from 
smoke, for the most part, is removed. Mr. Wilmot, of Isleworth, in writing on the 
advantages derived from some which he has had erected, says, “ After three months’ 
trial, I can now give you an account of the difference between your gas furnace and 
those on the old principle; the former has that decided preference that it only 
requires to be made known to be universally adopted. I put the lights on two 
vineries, sixty feet long (each), heated by hot water, on the 10th of January, the 
houses joining each other, with a glass partition between the boilers and pipes, both 
of the same construction ; as such we started fair. The result is, that from that 
time until this date, April 13, 1833, the gas furnace is one month earlier than the 
old ones, and both houses have as good a crop of grapes as I ever saw grow. In 
February I put the lights on two more vineries, of the same construction, but 
heated with flues instead of hot water, one is worked with the old furnace and the 
other with yours. Yours has again the preference of nearly one month ; and 
I have no doubt I shall cut grapes in it a month earlier than in the old one, and 
both houses have as good as I ever wish to have. The one I have attached to a pine 
house is certainly in the same proportions, but the smaller one you last sent me 
to try the experiment exceeds all. It is under a small boiler which works from 
three-inch pipes, in a house put up on purpose ; and, although but eight inches, I 
consider it capable of heating any house, provided it be worked with hot water pipes. 
The use of the gas furnace is the greatest saving that can possibly be invented, not 
only in the consumption of fuel, but of the labour ; while the uncertainty attending 
the old furnaces is entirely alleviated, and one person can attend to twenty of yours 
with more ease to himself than to four of the old ones. The certainty of being able 
to leave it twelve hours in early firing, without finding any material difference in 
the thermometer, speaks more for this valuable discovery than if I were to write a 
volume on the subject.” Mr. MTntosh, gardener at Claremont, writes as follows: 
“ The economy in fuel is more than one-third, nearly one-half. The trouble of 
attending them is next to nothing, as they are done up for the night at six o’clock 
in the evening ; and even in cold weather do not require any other attention till 
seven or eight o’clock next morning, and in mild weather not till five or six o’clock 
on the evening following. In consequence of the extraordinary degree of heat 
produced in the furnace (nearly 3,000 degrees of Fahr.), not only is the smoke 
consumed, after the fire has been burning for a short time, but all those noxious 
