them could be directed downward into a funnel tube communicating with the bilge.  The cocks of the glass tubes, as well as of the gauge cocks, should be furnished with stuffing boxes and with bottoms, unless the water enters through the bottom of the plug, which in gauge cocks is sometimes the case.  The glass gauge tubes should always be fitted with a cock at each neck communicating with the boiler, so that the water and steam may be shut off if the tube breaks; and the cocks 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 the pipe which it is desired to attach be put