The rate of flow of water through the apparatus is determined before the
experiment begins. This is done by deflecting the water for a certain
number of seconds into a graduate or by deflecting it into the small can
and weighing the water thus collected. The water is then directed into
the drain during the preliminary period. Meanwhile the main valve at the
bottom of the water-meter is opened, such water as has accumulated from
tests in preceding experiments is allowed to run out, and the valve is
closed after the can is empty. The meter is then carefully balanced on
the scales and the weight is recorded. At the beginning of the
experiment the water is deflected from the drain into the meter. At the
end of the period, while the water is running into the small can, the
water-meter is again carefully weighed and the weight recorded. Having
recorded the weight, the water is again deflected into the large meter
and what has accumulated in the small can is carefully poured into the
large meter through a funnel. If the meter is nearly full, so that
during the next period water will accumulate and overflow the meter, it
is emptied immediately after weighing and while the small can is filling
up. About 4 minutes is required to empty the can completely.
After it is emptied, it is again weighed, the water-current deflected
from the small can to the meter, and the water which has accumulated in
the small can carefully poured into the meter. All weights on the
water-meter, both of the empty can and the can at the end of each
period, are checked by two observers.