of this, and that is to test your steam gauge. If you know the steam
gauge is correct, you can make your safety valve agree with it; but
never try to make it do it till you know the gauge is reliable.

HOW TO TEST A STEAM GAUGE

Take it off, and take it to some shop where there is a steam boiler in
active use; have the engineer attach your gauge where it will receive
the direct pressure, and if it shows the same as his gauge, it is
reasonable to suppose that your gauge is correct. If the engineer to
whom you take your gauge should say he thinks his gauge is weak, or a
little strong, then go somewhere else. I have already told you that I
did not want you to think anything about your engine-I want you to know
it. However, should you find that your gauge shows when tested with
another gauge, that it is weak, or unreliable in any way, you want to
repair it at once, and the safest way is to get a new one; and yet I
would advise you first to examine it and see if you cannot discover the
trouble. It frequently happens that the pointer becomes loosened on the
journal or spindle, which attaches it to the mechanism that operates it.
If this is the trouble, it is easily remedied, but should the trouble
prove to be in the spring, or the delicate mechanism, it would be much
more satisfactory to get a new one.

In selecting a new gauge you will be better satisfied with a gauge
having a double spring or tube, as they are less liable to freeze or
become strained from a high pressure, and the double spring will not
allow the needle or pointer to vibrate when subject to a shock or sudden
increase of pressure, as with the single spring. A careful engineer
will have nothing to do with a defective steam gauge or an unreliable
safety valve. Some steam gauges are provided with a seal, and as long