September 2, 1836. ] 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
205 
not the case, for the water will circulate freely even when the pipes 
are all of the same level, and it is certain to do so with the rise indi¬ 
cated. The pipes in plant and fruit houses should be upon pillars 
that are built upon a firm foundation. If one of these pillars sink 
ever so little, and thus indicate a fall in the pipes, air is almost 
certain to find a lodgement, which in case of hard forcing will be the 
means of bursting the pipes if the boiler escapes damage. I have 
said that the pipes in the various houses to be heated should be on the 
same level if possible. Hot water will rush to the highest point first, 
and when the pipes are fixed on different levels considerable labour is 
occasioned in the regulation of the valves. When the houses, 
however, are on different levels, those on the lowest and nearest the 
boiler can be heated first, for the water will circulate and heat these 
before those on higher levels. After circulation has commenced on 
all the levels it is necessary to check the valves on the highest, or 
those on the lower ones will be robbed. In all such arrangements 
there is great difficulty in regulating the valves with any degree of 
certainty that the heat in all the houses will be as desired in the 
morning, for so much depends upon the force of the fire. The water 
may flow freely enough at times, and at others circulation may 
entirely cease, and the house, after banking the fire, become cold 
instead of warm ; but when the heating pipes are arranged on the 
same level throughout, the regulation of the valves is a simple matter, 
and the requisite heat can be depended upon with certainty. 
Bottom Heat PirES.— In garden structures for certain purposes it 
is often necessary to have what are known as top and bottom heat pipes. 
How frequently the pipes for these purposes are arranged on different 
levels ! It often happens that the former are 18 inches or 2 feet 
higher than the latter. To heat the lower pipes satisfactorily the 
valves require regulation, and even with the utmost care in this re¬ 
spect the water often fails to circulate in the lower ones, especially 
if those at a higher level take the lead. When circulation once com¬ 
mences in the bottom heat pipes and this is continued there is but 
little difficult}', but when it ceases the top pipes have frequently to be 
shut off until circulation is renewed. This state of things can be 
avoided by a little forethought and the practice of a different method. 
The whole of the pipes in each structure should be on the same level, 
and they will answer the same purpose as if some are placed higher 
than the others. Circulation would be even and constant through the 
whole without much trouble in the regulation of the valves. 
Dips in the Pites —These and awkward bends must be avoided, 
for they cause friction in the pipeB and are often the cause of failure. 
When pipes dip, say to pass a door, seldom indeed does the water 
circulate freely, especially if tkey are in houses only heated occa¬ 
sionally to keep out frost or to maintain a winter temperature of 40° 
to 45°. There is generally some trouble every time the pipes are re¬ 
quired warm. The flow will warm freely enough to the dip, but not 
beyond. Even when all the other houses are shut off, to force it into 
this particular one the task is by no means easy or safe. Air becomes 
deposited in the dip, and it is difficult to force it out. To avoid dips 
a few yards of extra piping may be needed, and perhaps a pair of 
extra valves, but the cost for these is in the end economy, and not 
only saves labour and anxieiy, but consumption of fuel. When 
arrangements cannot be completed without objectionable dips a half¬ 
inch air tap should be fixed into the flow pipe beyond the dip, where 
it rises to the same level as the flow pipe on the opposite side. This 
is not all, for another of these taps must be inserted on the top of the 
syphon at the extreme end of the flow pipe, so that it can be turned 
on at will. In each of these positions open air pipes should also be 
provided to insure safety. With open air pipes it is often impossible 
to drive the air out of them. Particulars on this point will be given 
under the heading of Air Pipes. For the present, suffice it to say 
that the tap beyond the dip should be turned on until the warm water 
runs out. Circulation cannot always be effected by this method, but 
the difficulty can gent rally be overcome by allowing the tap at the 
extreme end of the pipes to run until the warm water commences its 
return journey in the pipe below if placed one under the other. When 
circulation has once commenced there is but little difficulty in main¬ 
taining it until the valve is again closed, and it may give no trouble 
for some weeks if the water is circulated in the pipes every evening. 
Quantity of Piping Required. — How to arrive at the quantity of 
piping required in each individual structure is a very difficult matter 
for the inexperienced to determine. Many that should know better 
frequently over-estimate the heating surface of a given quantity of 
pipes, and only realise the mistake during severe weather and violent 
storms of wind. It must be borne in mind that a house fully 
exposed, say a span-roofed structure, will require a greater amount of 
piping to maintain a given temperature than one in a sheltered spot, 
a lean to for instance on the south side of a wall. Even these struc¬ 
tures with a building behind them are warmer and need less piping to 
maintain the requisite heat than one with the wall fully exposed to 
cooling influences. 11 also depends upon whether the pipes are exposed 
to the atmosphere of the house or placed in chambers covered with 
grating. Less piping is needed in the former than would be the case 
if the latter was adopted. We are not helped much in this matter 
by working out the amount of heat lost per square foot through the 
walls and glass according to the difference between the external and 
internal atmosphere. To estimate the cubic feet of air a house con¬ 
tains and the amount of heat required per minute to heat it to a given 
temperature according to the variations of the external atmosphere, is 
not only bewildering to the inexperienced, but also to the practical 
gardener. It is necessaiy that we should have a simpler method of 
arriving at a reliable decision than the complicated formulae pre¬ 
sented to us in nearly all works on heating by hot water. To place 
in any structure only sufficient piping when heated to its full 
capacity to maintain the temperature required is a great mistake. 
This I term insufficient heating surface, for the pipes have to be over¬ 
heated, and instead of economy, as may at first appear, proves a 
wasteful expenditure of fuel and injurious results to plant life, which 
can scarcely be estimated. In all structures, large or small, stove or 
greenhouse, double the quantity of piping actually required for the 
purpose should be provided. If two 4-inch pipes when made hot 
will insure the desired temperature no less than four 4-inch one 3 
should be employed, which will warm the atmosphere sufficiently 
without that drying scorching influence that would be the case with 
half the number. The size of a house and the purpose for which it is 
required, after the position has been taken into consideration, will be 
sufficient guidance for all thoroughly practised men to decide how 
many feet or rows of 4-inch piping is really needed to regulate with 
certainty the temperature without having to unduly heat the pipes. 
But this is not sufficient for those who have no knowledge of the sub¬ 
ject. If a temperature of 65° Fahr. at night during the winter is 
needed and the house (span-roofed) to be warmed is say 40 feetloDg, 
21 feet wide, 5 feet 6 inches high at the eave, and 12 feet high to 
the ridge fully exposed, it must have no less than eight rows of 
4-inch pipes—that is, four rows on each side and across the ends with 
the exception of the doorways. Half the number would have to be 
very highly heated to be certain of that temperature. At times it 
could not be kept up. A house of this description will contain 
7350 cubic feet of air, the volume of which is found in the following 
manner :— 
Find the area of A E D C, then the area of A B C ; add the two 
areas together, and multiply the sum by the length of the house, and 
Fig. 28. 
the product will be the number of cubic feet of air contained in the 
house. Area of A E D C=21 X 5|- = 1154. Area of A B C 
= 4 of 64 X 21 = 68j-. Therefore area of end B A E D C = 1154 
+ 08i = 183J. The volume of air=l83J X 40 (length of the 
house) =7350 cubic feet. A house of these dimensions will need 
eight rows, or 428 feet of 4-inch piping to heat it thoroughly. 
Divide 7350 by 428 and we obtain 17 one-fifth. Thus, if the required 
temperature be 65° Fahr. one foot of piping will heat 17 one-fifth 
cubic feet of air. But if an intermediate temperature be required, say 
55° Fahr., 1 foot of piping will be necessary for every 20 cubic feet 
of air. Again, if a still lower temperature is required, for instance 
45° Fahr., 1 foot of piping would be required for every 25 cubic feet 
of air. If the exclusion of frost merely is needed 1 foot will be suffi¬ 
cient for every 32 cubic feet of air. 
Packing the Joints.— A difference of opinion exists about the best 
and most durable material for packing the joints of hot-water pipe3. 
The old plan of making the joints with iron tilings and sal ammoniac 
intermixed to insure the metal rusting has been condemned. The 
arguments used by the advocates of other methods are not strong, but 
