an hour before starting
a test and for a like period before its close, the height of the
throat plate and the speed of the grate being the same during
both of these periods.

8. RECORDS

A log of the data should be entered in notebooks or on blank sheets
suitably prepared in advance. This should be done in such manner that
the test may be divided into hourly periods, or if necessary, periods of
less duration, and the leading data obtained for any one or more periods
as desired, thereby showing the degree of uniformity obtained.

Half-hourly readings of the instruments are usually sufficient. If there
are sudden and wide fluctuations, the readings in such cases should be
taken every 15 minutes, and in some instances oftener.

The coal should be weighed and delivered to the firemen in
portions sufficient for one hour's run, thereby ascertaining the
degree of uniformity of firing. An ample supply of coal should
be maintained at all times, but the quantity on the floor at the
end of each hour should be as small as practicable, so that the
same may be readily estimated and deducted from the total
weight.

The records should be such as to ascertain also the consumption
of feed water each hour and thereby determine the degree of
uniformity of evaporation.

9. QUALITY OF STEAM[67]

If the boiler does not produce superheated steam the percentage of
moisture in the steam should be determined by the use of a throttling or
separating calorimeter. If the boiler has superheating surface, the
temperature of the steam should be determined by the use of a
thermometer inserted in a thermometer well.

For saturated steam construct a sampling pipe or nozzle made of one-half
inch iron pipe and insert it in the steam main at a point where the
entrained moisture is likely to be most thoroughly mixed. The inner end
of the pipe, which should extend nearly across to the opposite side of
the main, should be closed and interior portion perforated with not less
than twenty one-eighth inch holes equally distributed from end to end
and preferably drilled in irregular or spiral rows, with the first hole
not less than half an inch from the wall of the pipe.

The sampling pipe should not be placed near a point where water
may pocket or where such water may effect the amount of moisture
contained in the sample. Where non-return valves are used, or
there are horizo