safety valve is set at one hundred and ten pounds, this pressure of cold
water will be sufficient to test the flues.

Now, suppose you are out in the field and want to test your flues. Of
course you have no hydrant to attach to, and you happen not to have a
force pump, it would seem you were in bad shape to test your boiler with
cold water. Well, you can do it by proceeding in this way: When you
have expanded and beaded all the flues that were leaking, you will then
close the throttle tight, take off the safety valve (as this is
generally attached at the highest point) and fill the boiler full, as it
is absolutely necessary that all the space in the boiler should be
filled with cold water. Then screw the safety valve back in its place.
You will then get back in the firebox with your tools and have someone
place a small sheaf of wheat or oat straw under the firebox or under
waist of boiler if open firebox, and set fire to it. The expansive
force of the water caused by the heat from the burning straw will
produce pressure desired. You should know, however, that your safety is
in perfect order. When the water begins to escape at the safety valve,
you can readily see if you have expanded your flues sufficiently to keep
them from leaking.

This makes a very nice and steady pressure, and although the pressure is
caused by heat, it is a cold water pressure, as the water is not heated
beyond one or two degrees. This mode of testing, however, cannot be
applied in very cold weather, as water has no expansive force five
degrees above or five degrees below the freezing point.

These tests, however, are only for the purpose of trying your flues and
are not intended to ascertain the efficiency or strength of your boiler.
When this is required, I would advise you to get an expert to do it, as