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43
the treated floor with a hard broom, and the figures at the bottom of
the diagram represent the number of weeks which had elapsed from
the day on which the dust allayer was applied.
During the whole of the period recorded on the diagrams, the
floors treated with the "dust altayer " were unwashed.
Of the dust allayers used two, Nos. 2 and 3, were cily substances
which it will be seen gave excellent results. The other, No. 1, is
more expensive than Nos. 2 and 3 and its effect is much more quickly
lost. Turning now to the results, they may be summarised as
follows—
No. 1 Substance.
On a hard wood floor, the restraining influence upon dust
is as great at the end of four weeks as floor washing at the end
of two days.
On a soft wood floor its influence for practical purposes is lost
at the end of a fortnight or three weeks, but is better then
than floor-washing after two days.
No. 2 Substance.
On a hard wood floor its effectiveness for nine weeks was
absolute. At the end of that period its restraining influence was
rapidly lost, but to the end of the 15th week the results are
better than those obtained from floor washing after three days,
and to the end of the 19th week not worse.
On a soft wood floor, the results were less constant, but on
one occasion only during 13 weeks was it observed to fail to keep
the dust from rising in anything but negligable quantities, and
at the end of this period was better than floor washing after two
days.
b