ks should be so made as to admit of the
tubes being blown through with steam to clear them, as in muddy water they
will become so soiled that the water cannot be seen. The gauge cocks
frequently have pipes running up within the boiler, to the end that a high
water level may be made consistent with an easily accessible position of
the gauge cocks themselves. With the glass tubes, however, this species of
arrangement is not possible, and the glass tubes must always be placed in
the position of the water level.

474. Q.--What is the proper material of the pipes in steam vessels?

A.--Most of the pipes of marine engines should be made of copper. The steam
pipes may be of cast iron, if made very strong, but the waste water pipes
should be of copper. Cast iron blow-off pipes have in some cases been
employed, but they are liable to fracture, and are dangerous. The blow-off
and feed pipes should be of copper, but the waste steam pipe may be of
galvanized iron. Every pipe passing through the ship's side, and every pipe
fixed at both ends, and liable to be heated and cooled, should be furnished
with a faucet or expansive joint; and in the case of the cast iron pipes,
the part of the pipe fitting into the faucet should be turned. In the
distribution of the faucets of the pipes exposed to pressure, care must be
taken that they be so placed that the parts of the pipe cannot be forced
asunder, or turned round by the strain, as serious accidents have occurred
from the neglect of this precaution.

475. _Q._--What is the best mode of making pipes tight where they penetrate
the ship's side?

_A._--In wooden vessels the pipes where they pierce the ship's side, should
be made tight, as follows:--the hole being cut, a short piece of lead pipe,
with a broad flange at one end, should be fitted into it, the place having
been previously smeared with white lead, and the pipe should then be beaten
on the inside, until it comes into close contact all around with the wood.
A loose flange should next be slipped over the projecting end of the lead
pipe, to which it should be soldered, and the flanges should both be nailed
to the timber with scupper nails, white lead having been previously spread
underneath. This method of procedure, it is clear, prevents the possibility
of leakage down through the timbers; and all, therefore, that has to be
guarded against after this precaution, is to prevent leakage into the ship.
To accomplish this object, let th