a test may easily be found by using
an ordinary wheelbarrow and a platform scales, arranged as in
figure 1. At each side of the scales build an incline with its top
level with the top of the platform, but take care not to have
either one touch the platform. Set the empty wheelbarrow on the
scales, run the movable weight or poise out until it exactly
balances the weight of the barrow and lock it in position with the
thumbscrew.

Next, put weights on the scale pan _A_ to correspond to a net
weight of 250 or 300 pounds of coal. Fill the barrow with coal, run
it on the scales, and add coal or take off coal until the scales
balance. This is easily done by having a small pile of coal _B_
beside the scales. If the weights on the scale pan represent, say,
300 pounds, the net weight of coal in the barrow is exactly 300
pounds. This coal is wheeled in front of the boiler and dumped on
the clean floor, and the barrow is returned for another load.

[Illustration: _Fig. 1._

1 _Set to balance tare of wheelbarrow_
2 _Add to balance net weight of coal_]

Each time the barrow of coal is weighed on the scales and taken to
the boiler being tested, a tally mark should be made on a board
nailed to the wall beside the scales. Each tally mark represents
300 pounds of coal, since the amount of coal in the barrow is
adjusted at each weighing, so that the scales just balance. At the
end of the test, therefore, the number of tally marks is multiplied
by 300, and the product is the weight of coal used, provided it has
all been fired; but if any coal remains in front of the boiler at
the close of the test, it must be gathered up and weighed, and its
weight must be subtracted from the total weight indicated by the
tally marks to get the number of pounds of coal actually fired. You
should, of course, start the test with no coal in front of the
boiler.

Care must be taken not to forget to make a tally mark each time a
barrow of coal is run off the scales. By setting the scales so as
to show any net weight, such as 250 or 300 pounds, and making each
barrow load exactly this weight, much time is saved, as it is
unnecessary to change any of the weights or the position of the
rider on the scale beam.

If the coal used in the test is to be analyzed, take a sample of
from 4 to 6 pounds from each barrow and throw it into a box near
the scales. Do this _before_ the coal is weighed. These small
amounts from the various barrow loads will then give a