355 
THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, September 11, 1860. 
is porous and damp. A pound of dry wood will heat thirty-five 
pounds of water from 33° to 212°; but a pound of the same 
wood in a moist or fresh state will not similarly heat more than 
twenty-five pounds. The value, therefore, of different woods for 
fuel is nearly inversely as their moisture; and this may be readily 
ascertained by finding how much a pound weight of the shavings 
of each loses by drying, during two hours, at a temperature 
of 212°. > p 
The above are the average of results obtainable in a common, 
well-constructed furnace. By a complicated form of boiler, 
perhaps, a small saving of fuel in obtaining the same results mav 
be effected ; but it will be found, generally, that the original cost 
•of apparatus, and the current additional expenses for repairs, 
will more than exceed the economy of fuel. 
Flues for imparting heat to hothouses are, for the most part, 
superseded by either tanks or hot-water pipes; but where re¬ 
tained, the top should be formed of iron plates, these admitting 
the heat most readily into the house, and, consequently, requiring 
a less consumption of fuel. If it be desirable to have a covering 
for the flues that will retain the heat longer, as when the fires are 
made up at night, this may be readily accomplished by putting 
a row of the thick square paving tiles on the top of the whole 
length of the flue an hour or two before the houses are finally 
•closed. 
Hot water in a tank is superior to the same source of heat in 
pipes, because it is not liable to freeze; and it is preferable to 
abeam, because its heating power continues until the whole mass 
of water is cooled down to the temperature of the house ; whereas 
steam ceases to be generated as a source of heat the moment the 
temperature falls below 212°. 
It steam be employed, Mr. Tredgold has given the following 
rules for calculating the surface of pipe, the size of the boiler, 
the quantity of fuel, and the quantity of ventilation required for 
a house 30 feet long, 12 feet wide, with the glass 4 feet high in 
front; vertical height of the glass roof 8 feet; length of the 
rafters 14 feet; height of the back wall 15 feet. The surface of 
glass in this house will be 720 feet superficial—viz., 540 feet in 
the front and roof, and 180 feet in the ends. Now, half the 
vertical height, 7 ft. 6 in., multiplied by the length in feet, and 
added to 1£ time the area of glass in feet, is equal to the cubic 
feet of air to be warmed in each minute, when there are no 
double doors—that is, 7'5 * 30 + if * 720=1305 cubic feet. 
But in a house with wooden bars and rafters, about one-tenth of 
this space will be occupied with wood-work, which is so slow a 
conductor of heat, that it will not sufier a sensible quantity to 
escape. Therefore, 130 feet may be deducted, leaving the quantity 
to be warmed per minute = 1175 cubic feet. 
To ascertain the surface of pipe required to warm any given 
quantity of air, multiply the cubic feet of air to be heated per 
minute by the difference between the temperature the house is 
to be kept at, and that of the external air in degrees of Fahren¬ 
heit’s thermometer, and divide the product by 2T, the difference 
between 200, which is the temperature of the steam pipes, and 
the temperature of the house; the quotient will be the surface 
of cast iron pipe required. 
Now, in the house, the dimensions of which are above given, 
if the lowest temperature in the night be fixed at aO°, and 10° are 
allowed for winds, and the external air is supposed to be at zero, 
or 0 of Fahrenheit, then 1175 multiplied by 60°, and the pro¬ 
duct divided by 2’1, the difference between 200 and 60, will give 
us the quotient 236 = to the surface of pipe required. Now the 
house being 30 feet long, five pipes of that length, and five inches 
in diameter, will bo about the proper quantity. 
If hot water be employed instead of steam, the following pro¬ 
portions and information, obtained from Mr. Rendle, may be 
adopted confidently as guides. In a span-roof propagating-house, 
40 feet long, 13 feet broad, 7 feet high in the centre, and 4 feet 
high at the two fronts, having a superficial surface of glass 
amounting to 538 square feet, Mr. Rendle has a tank of 83 feet 
long, running round three sides of the house, 4 feet wide, and 
about 8 inches deep ; and, consequently, capable of containing 
nearly 300 cubic feet of hot water, though only half that quantity 
is used. This is closely approaching to the size pointed out 
according to Mr. Tredgold’s formula. The mean temperature of 
a hot-water tank will never be much above 160° ; so that, for the 
sized house mentioned by that skilful engineer, the divisor must 
be 2T times the difference between 160° and 60°, which gives as 
the quotient 335 cubic feet. 
The tank in Mr. Rendle’s propagating-house is built of bricks 
lined with Roman cement; and if the temperature of the tank 
at the time of lighting the fire be 90°, the temperature of the 
atmosphere of the house 67°, and the temperature out of doors 
.50°, the quantity of small coal, or breeze, required to raise the 
temperature of the water to 125° is 28 lbs. In twelve hours the 
water cools, after the fire has been extinguished, from 125° to 93°. 
vVhen steam is employed, the space for steam in the boiler is 
easily found by multiplying the length of the pipe iu feet, by th* 
quantity of steam in a foot in length of the pipe. 
Interior dia¬ 
meter of pipe 
in inches. 
1 . . 
li . . 
2 . 
2i 
3 
4 
5 . . 
6 
7 
8 
9 
10 
Decimal parts of 
a cubic loot of 
steam in each 
foot of pipe. 
. -00545 
. . -01225 
•02185 
. . -034 
•049 
. . -0873 
•1363 
. . T964 
•267 
. . -349 
•442 
. . -545 
In the above-noticed house, the length of pipe, 5 inches in 
diameter', is 150 feet, and these multiplied by 1'363 = 20'5 cubic 
feet of steam ; and as the pipe will condense the steam of about 
one and one-third cubic foot of water per hour; therefore, the 
boiler should be capable of evaporating 1J cubic feet of water 
per hour, to allow for unavoidable loss. In the extreme case of 
the thermometer being at zero, the consumption of coals to keep 
up this evaporation will be 12| lbs. per hour .—(Tredgold on 
Warming and Ventilation.) 
These calculations are all founded upon the supposition that 
the condensed water is returned to the boiler whilst hot; but if 
this cannot be effected, then one-twelfth more fuel will be re¬ 
quired. The boiler for the supply, either of steam or hot water, 
should be covered with the best available non-conductor of heat, 
and this is either charcoal or sand. A case of brickwork, with 
pulverised charcoal between this and the boiler, is to be pre¬ 
ferred to any other. A boiler having a surface of 70 feet exposed 
to the air in a temperature of 32° requires an extra bushel of 
coals to be consumed per day, to compensate for the heat radiated 
and conducted from that surface ; and the smaller the boiler the 
greater is the proportionate waste. 
The smaller the boiler and the fireplace, compatible with effi¬ 
ciency, the greater is the economy. We can tell the gardener, 
also, most decidedly, that the total size of the boiler has nothing 
to do with that efficiency ; the only point to be secured is, that 
a sufficient surface of the boiler be exposed to the fire. The 
following table shows the amount of boiler surface which must 
be exposed to the fire to heat given lengths of pipe, respectively 
4 inohes, 3 inches, and 2 inches in diameter 
Surface of boiler exposed 
4-inch 
3-inch 
2-inch 
to the fire. 
pipe 
pipe 
pipe. 
ft. 
ft. 
ft. 
square feet will heat. 
200 
or 
266 
or 
400 
5* 
33 33 • • • 
300 
400 
600 
7 
» 33 • • * 
400 
533 
800 
8* 
33 33 • • . 
500 
666 
1000 
12 
33 33 • • 
700 
33 
933 
1400 
7 
33 33 • . • 
1000 
33 
1333 
33 
2000 
To prevent the scale, or limy crust in a boiler, which is often so 
troublesome, dissolve in the water at the rate of one ounce of sal 
ammoniac (muriate of ammonia) to every sixty gallons. Do this 
twice in the year ; as, in October and April. 
The surface of the pipes should be painted black, because 
surfaces of this colour give out more heat in a given time than 
any other.—J. 
(To be continued.) 
Gardeners’ F£te at Paris. — On the 30th of August 
was the fete of the gardeners, whose patron is Saint Fiacre—a 
rather strange selection, when we remember that a gardener and 
a coachman are generally considered to have little in common, 
except in families whose desire for gentility outruns their mean*. 
However, the coachmen have something to do with the matter 
