Rain-water pipes are made almost as thin as the process of casting

will allow, and therefore such pipes are peculiarly liable to fracture
during carriage. When, however, they are fixed in place the pipes
are strong enough for their purpose, and if kept painted will probably
last as long as the building to which they are attached; but if not
cast concentric, the thin places will soon be corroded away and the
pipes rendered useless. Rain-water pipes have socket joints and are
sold by measure of length, and not by weight. In specifying such
pipes the bends, swan-necks (almost always needed to clear projec-
tions on buildings), and enlarged head-castings which are required
should be described.
Wrought-iron pipes (as distinct from tubes) are made of sheet-iron
from ^ in. to 3^ in. thick riveted, and are used for various purposes
where light, strong pipes are required. Thus, they are used some-



Part II.] Wrought-iron Pipes. Tubes.
