a handbook of the mosquitoes of north america - Systematic Catalog ...

MOSQUITO REDUCTION 69
in oil and anchored in ponds has the same drawbacks. Fine
sand soaked in oil and sowed broadcast over ponds has given
satisfactory results. As the sand falls on the water or sinks
through the vegetation to the water surface the oil is given off
and leaves a good film.
In large lakes, ponds, etc., where the margin and flotage is
not easily accessible except by small boats a large tank fitted
(Courtesy of the Hudson County, IV. J., Mosquito Commission.)
FIGURE 20. A power outfit used in oiling large areas accessible to road-
ways.
with a pump to give the necessary pressure may be employed.
The pump may be used to force the oil out directly or it may
be used to compress the air. If air compression is employed,
pumping is not continuous and in general a better and more
even spray may be obtained.
In all oiling work, the most essential points are the use of
a good, free running, toxic oil, good equipment, and extreme