271 
THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Febefary 5, 1861. 
be heated, the flow-pipe should be as near the top as will secure 
that pipe being kept full, and the return-pipe should enter near 
the bottom. These matters secured, the flow and return pipes 
in the house may be one above another, or both on the same 
level or nearly so. We think in the latter case the return-pipe 
gives off more heat. When the boiler is close and sunk beneath, 
the level of the heating-pipes some feet, the boiler will always be 
sure to be full of water so long as there is water in the pipes. 
If there is an open cistern at the highest part of the pipes, fresh 
water may be given there. Some prefer a cistern on purpose 
near the boiler placed higher than any of the pipes, and a pipe 
going directly from it to the bottom of the boiler. In this 
latter case an open air-pipe, such as is used for gas-burners, 
should be inserted in the highest point of the pipe to prevent air 
accumulating there; and in very small places such air-pipe 
should go outside the house, as an extra strong fire may cause 
the water to be thrown out in boiling hot jets. Under similar 
circumstances, also, a very small cistern connected with the 
flow-pipe may easily be made to run over, when the attendant 
thinks of nothing but keeping a strong fire burning. When 
heat is once raised, a small smothered fire will keep it up. 
EXPANSION OP WATER. 
The cause of this is the expansion of water by heat. I cannot 
just now lay my hands on some memoranda as to the determi¬ 
nate expansion of water as it gets near the boiling-point. One 
singular fact about water ought to render the gardener very 
careful of a double expansion, as it may be called—expansion by 
cold and expansion by heat. By the first, hot-water pipes in 
houses not worked in winter are often injured by frost, and in 
such cases the pipes should be left empty. Water has its 
greatest specific gravity or density at 42° Fabr. Whether it rise 
or fall below that in temperature it expands, becomes lighter and 
wants more room, and hence it is that ice keeps at the surface. 
The bulk is not increased in a regular manner, according to the 
degrees of the thermometer; but whatever number of degrees it 
falls or rises from 42° the increase in bulk will be the same. 
Thus the bulk at 37° will be 1000.55, and at 36° 1000.56 ; but 
at 32° it will be 1000.66, at 31° 1000.70, and at 30° 1000.74. 
Thus, also, on the principle referred to, the specific gravity of 
water at 30* will be the same as if it were at 54°; and water ?t 
10° will be expanded as much as if it were at 74°. As we raise 
the temperature we increase the expansion or lightness, but not 
in arithmetical progression ; for whilst at 74° each addition of 
a degree would give about .00014 of an increase, at 102° it would 
give .00025 for each degree; and at 182° it would, for every 
degree in addition, expand .00036, according to Mr. Tredgold. 
EXPANSION OF PIPES. 
The above matters should be kept in mind in winter, as, if 
the pipes are of metal, they will contract in frost, whilst the 
water in them expands. All pipes will expand by heat, but all 
metals will expand more than earthenware. Metal pipes con¬ 
taining water about 200°—and it should seldom be hotter—will 
expand about one inch in 100 feet. It is better, therefore, to 
have them slung loose than to have them firmly bedded or close 
fixed. 
MAKING JOINTS. 
On the above account when made of easily expanded materials, 
and crammed too tight and full, openings either will be made 
or the joint will fly. All joints that come in contact with the 
fire are best done with iron filings. For flange joints fixed to the 
boiler there, vulcanised Indian-rubber tightly screwed up will 
do ; but though it may be prejudice, I prefer for such places flange 
or socket joints, iron filings, cement composed of one part sal 
ammoniac finely powdered, added to about ninety parts of finely 
powdered iron filings. A small portion of this is put into an 
iron vessel, a»d enough water given to make a thick mixture as 
wanted, as it will soon get too hard for use. A band of tow or 
rope yarn is incorporated with it, and then by means of a thin 
chisel or spatula, is driven home to form the bottom of the 
joint. Continue the process until the joint is firmly and securely 
filled. The mixture takes such hold of the iron, that taking it 
out of the joint afterwards is next to an impossibility. Some 
artificers use a little sulphur in addition, but I cannot say it is 
any advantage. The joinings of Southwark bridge were thus 
formed :—one ounce of flowers of sulphur, two ounces of sal 
ammoniac, and sixteen ounces of iron filings pounded fine and 
dry in a mortar. When wanted, take one-part of this mixture, 
and add twenty-parts more of clean iron filings, and use water 
to bring to suitable consistence as above. For all other joints not 
in contact with the fire, I would just as soon have the joints of 
pasteboard, tow, or rope yarn, saturated with red lead, driven 
firmly home. These can easily be taken to pieces by apply¬ 
ing burning charcoal below the joints to soften them. In 
cases of great pressure the iron-filings joint would be best. 
When pipes of sheet-iron, galvanised iron, copper, &c., are made 
to fit each other by flanges, then pasteboard, and a mixture of 
red and white lead on each side, make capital joints when 
screwed together. In small houses when such thin pipes are 
used for water, and are merely made to fit into each other at the 
ends without any sockets, a mixture of red and white lead, 
made a little thin with a little boiled linseed oil, put on both 
sides of a piece of flannel, or cotton, will make a good joint, or 
soldering may be had recourse to—in fact, lead joints do very 
well if a short distance from the fire. Earthenware pipes with 
sockets may be first done with a bottom layer of tow and red 
lead, and the rest of the joint be made with cement. 
MATERIALS FOR FIFING. 
All things considered, there is nothing better on the whole 
than cast-iron pipes. Some other metals, as copper, may be 
better conductors and radiators of heat; but iron is very fair as 
respects these properties, and has the advantage of cheapness 
and strength. All earthenware in proportion to its porosity is 
deficient in conducting and radiating power. Heat when once 
communicated, however, must be given off until an equality is 
reached between the heated body and surrounding objects. Bad 
radiators are, therefore, longer in giving out heat; but, just on 
that account, they give it out much longer before they are cooled. 
The same thing may be said of thin copper and ordinary-sized 
cast-metal pipes. The latter will keep hot longest, and radiate 
heat freely too. 
We naturally like to see the effects quickly of the fire 
we light below the boiler; and, therefore, the colour of the 
piping is important. A light-coloured pipe may be quite as hot 
as a dark one, but the heat will not be thrown off in anything 
like the same proportion as to celerity. The brighter and whiter 
the colour, the slower the radiating power. The nearer the pipes 
are to black, the quicker will they part with their heat. Black 
is not only the best radiator, but the best absorber of heat. A 
simple example will make this clear. In many parts of the 
north, “black jacks,” or vessels of dark earthenware, are pre¬ 
ferred by the labourers’ wives for teapots. In London, me¬ 
chanics wives like to show off their bright Britannia-metal tea¬ 
pots. The properties of the two vessels as respects absorbing, 
conducting, and radiating heat, are very different, and yet good tea 
is made in both by altering the management. The country lady 
heats her pot with boiling-water rinsing or other means, puts in 
the tea and covers with a sufficiency of water to draw out its 
virtues, and then places her pot close to the fire. The heat that 
thus would be thrown off from one side of the teapot is more 
than counteracted by the heat absorbed from the side next the 
fire, and thus the fluid within is kept to within a few degrees— 
say 10° or 15° of boiling water. The brisk mechanic’s wife 
brings her elegant tea-caddy, puts in her tea, and pours the 
boiling water on it at the table before everybody, and allows her 
pot to stand there. The bright polished surface keeps the heat 
in, and thus draws the virtue out of the tea. Even if she placed 
the pot near the fire, which she will not do because it might 
tarnish the brightness, she would not gain a vast advantage, 
because the bright surface would reflect the heat considerably 
instead of absorbing it. If the village dame went through this 
mode of making tea with her black teapot, and set it at once on 
the table, her tea would be sorry stuff, because the water inside 
would cool too quickly. The matter may easily be tried by two 
such pots, and marking how much sootier the boiling water cools 
in the one than the other. Two metal teapots may serve for the 
same experiment, the one bright scoured, and the other painted 
black. Hence, as we wish to get heat quickly and regularly from 
our pipes, a black or dark colour is the best—such as is formed 
by oil and lamp black. 
DIRECTION OF PIPES. 
From an open boiler, they should be on a level with it; from 
a close boiler, they may go to any reasonable height. For 
instance: From a boiler in the cellar a flow and return pipe 
may go to the garrets in a mansion, and may be filled there from 
an open cistern. From that flow and return branches may go 
to every room in the house. From such a close boiler, and at 
