HEATING BY HOT WATER. 173 
so that this need not be considered farther. An iron 
cement or ‘‘rust-joint,” composed of iron filings, sal- 
ammoniac, and water, with a little sulphur, was much 
employed at one time, but though very lasting, and usually 
tight, the rust eating into the metal and joining the pipes 
immoveably in time, such joints frequently ‘ weep” a 
good deal at first, and after a time frequently split the 
sockets, as the mixture expands considerably in rusting. 
India-rubber rings have also been much used and 
recommended for jointing pipes, but though very useful 
and easily fixed when they fit all right, and the pipes 
and sockets are uniform in size, great difficulty is often 
experienced in forcing them into small sockets at all. In 
fact, I have known two or three men to ‘‘shove” the 
end of a house out bodily trying to get a ring in. Even 
when in, they sometimes leak, and after a few years the 
heat renders the rubber hard and perished, and then if 
cracks and leaks. On this account the joints are frequently 
filled up with Portland cement above the rings. 
But decidedly the best and most lasting joints for socket- 
pipes, at least in the writer’s considerable experience, are 
those made with pure Portland cement alone. This 
material is very easily mixed and applied, while it hardens 
or “sets” almost immediately, and if properly done will 
last a lifetime, if not for ever. Even if it is ever desired 
to take the pipes apart, all that is necessary is to break 
through the hard face of the cement with a narrow steel 
chisel, wriggle the pipes about a little, and away they come, 
totally uninjured. 
The sockets should be packed about half full of rope-yarn 
first—indeed, lin. to 14in. of cement is sufficient, provided 
