18 
BULLETIN L204, V. S. DEPARTMENT OF AGRICULTURE. 
air currents created by the plane. In Figure 15, in which the plane is 
flying about 15 feet above the cotton plants, it will be noted that to 
the point marked a the dust cloud has followed a regular form, and 
has not yet touched the cotton plants. During this time it is still 
being carried around the spiral and is rolling over and over. At a, 
however, the poison is beginning to catch in the cotton plants, and at 
the vd^xv of this picture nearly all the poison is feeling the influence 
of the plants. Figure 16 is a continuation of the same cloud, merely 
looking farther to the rear. In this view the dust is spread in a fairly 
uniform layer over a swath gradually increasing in width as distance 
from the plane is increased, and distributed among the plants, with 
only a small amount of material going off in the air above. These 
Fig. Hi. — After taking the view shown in Figure 15, the photographer Immediately 
snapped this picture lnokini: over the tail of the photographic plane. Thus this view- 
shows a continuation of the same <iust cloud being released in Figure 15, hut consider- 
ably to the rear of the dusting plane. Note how the cloud is spread out among the 
plants over an area about :.'•"» feet wide. At the time this picture was taken the 
dusting plane had just laid down such a (loud nearly 3 miles long. 
photographs were taken about 11 a. m., with an 8-mile breeze blowing, 
which would render absolutely impossible any effort to dust cotton 
with ordinary ground dusting machines. Figure 17 further illus- 
trates the behavior of the dust leaving the plane. In this it will be 
noted especially that the dust cloud has maintained its spiral shape 
to the point marked ./. but is then quickly flattened out among the 
cotton plants. 
INFLUENCE OF VARIOUS AIR CONDITIONS. 
In the studies on operating at different times of the day and under 
different air conditions, wind records were kept throughout the ex- 
perimental period which' showed that, as a general ride, there was a 
