fair average
sample of the coal used during the test.

The condition of the furnace should be the same at the end of the
test period as at the start. Therefore, at the moment the test is
begun, observe the thickness of the fuel bed and the condition of
the fire. If the fire was cleaned, say, an hour before the test
began, see that it is cleaned an hour before the time when the test
is scheduled to end. If the coal was fired, say, eight minutes
before the test started, the last coal used during the test should
be fired eight minutes before the end of the test. The object of
these precautions is to insure the same conditions at start and
finish, as nearly as possible; otherwise, the coal weighed will not
be the same as the coal consumed.

MEASURING THE FEED WATER.

The quantity of water fed to the boiler during the test may be
found by metering or by weighing. A reliable water meter is
recommended for this work. There are a number of good makes, of
different types, such as:

1. Venturi meter.

2. Weir or V-notch meters.

3. Diaphragm meters.

4. Displacement meters.

5. Water weighers.

The best form of meter to use in any particular case depends on the
local conditions in the plant; but _every plant should be provided
with a permanently installed meter of some type_. The displacement
form of meter should be used only with cold water, however.

If there is no meter or water weigher in the plant, the feed water
used during the test can be measured by the three-barrel
arrangement illustrated in figure 2.

Obtain three water-tight barrels, and set two of them close
together on a platform directly over the third, leaving about 12
inches above barrel 3 in which to fit the valves _V_ and the
nipples in the bottoms of barrels 1 and 2. Near the top of each of
the barrels 1 and 2 screw a 1-inch overflow pipe _O_.

Run a pipe _P_ from the city main or other source of supply above
barrels 1 and 2, and put a valve _A_ on the pipe leading to each
barrel. From barrel 3 run a suction pipe to the feed pump that is
to pump water to the boiler to be tested. It is best to have a
by-pass from the usual water supply direct to the feed pump, or to
another pump connected to the boiler, so that in case of any
trouble with the testing barrels, the regular operation of the
boiler may be resumed without shutting down.

The next step is to fill barrels 1 and 2 with water until they
overflow at _O_. This water should b