The citizen., 1910-04-01

III SldIIHS lnat the question of the
suppression of road dust has been.
within the last few years, subject
Oh constant attention on the mart of
the French Government, through the
department of Public Works, Consul
w. ii. Hunt, of st. Etienne. sums up
the results of experiments as follows:
hitherto water alone was EMPLOYED
1or the purpose, but its effect was
only transitory, and the treatment
mad to be renewed every morning.
This half measure nevertheless gave
satisfaction until automobiles and
road tramways began to circulate.
creating, by their speed. an amount
OF dust as annoying as it was preyi-
ously unknown. A report has Just
Deen presented to the Minister of
Public Works, reviewing the advan-
tages and disadvantages of four
methods, considered as more or less
effective in laying dust-a coating of
crude tar mixture, heated petroleum,
solution of water and salts, and con-
struction of a beton and tar surface.
To the mixture of crude tar, tar
oil in the proportion of ten per cent.
is added to render it more fluid, and
before sprinkling it on the road cer-
tain conditions are necessary-the
road should be more or less cylindric
in shape, recently macadamized. dry
and swept of all dust. The tarring
should be done in dry and warm
weather, while no circulation of vehi-
cles should be allowed until the coat
ing is sufficiently dry.
The durability of the coating varies
as to the time of the operation,
whether in summer, autumn or win
ter. II done in the last two seasons,
the tarring seldom resists until the
following spring. Very frequently it
disappears at the end of two or three
months, leaving in it's place an
abundant supply of disagreeable mud.
AS long as the coating of t. endures,
the road bed is guaranteed against
wear and tear, but once it gets diluted
the road becomes deteriorated all the
more rapidly, as the mud retains the
water with greater facility. Although
the quantity of the tar mixture en-
ployed varies with the absorbent ma
ture of the road, a proportion of two
pounds to the square yard is consid-
cred sufficient. Frost does not seem
to have any evil effects on tarring,
but great heat may soften it and rem
der it slippery. The cost of tarring
is estimated at three cents per square
yard.
The second method, or that of
petroleum heated to boiling point, is
used in the north of France and
around Paris. The variety of oil en-
ployed is that known under the name
of "mazout. The oil is placed in
reservoirs similar to ordinary water
ing carts and sprinkled over the
roads, previously swept. 1t is allowed
to cool, after which the dust is swept
back over it again; the dust is ef-
fectively laid and will not adhere to
the car wheels. Unfortunately, au-
tumn rains rapidly destroy this coat
ing. In dry climates, however, the
above two methods are very effective
against dust.
The saline mixture consists in
either plain sea water on a solution
of certain salts (chloride of calcium
or chloride of magnesium), which
from their hygrometric properties
maintain on the road the humidity of
the atmosphere, thus prolonging the
effect of ordinary watering. Infor-
nation, however, is wanting as to the
results of the experiments.
Westrumite is tar rendered soluble
in water by the addition of ammonia
and other cheap products. 1t is par
ticularly useful in preparing race
track, as its effects are limited as to
duration.
The fourth and last method is cost
1y and has not yet been put into op-
Grafton to any extent in France. 1t
consists in constructing the road with
beton or concrete, into which tar is
incorporated Further experiments
are about to be made by the Govern
ment, not only for the purpose of
adopting the best dust-laying SUBJ
stance, but also for determining the
effect of the operation itself on the
oads.