132 OHIO EXPERIMENT STATION: MONTHLY BULLETIN 



DETAILS OF APPLYING THE DUST 



The dusting plane left McCook Field shortly after noon on 

 August 3, 1921, and flew to a previously selected landing field about 

 a mile and a quarter distant from the grove to be treated. There 

 the hopper was filled and the work of applying the dust began. 



The meteorological conditions were ideal. The sunlight was 

 excellent for photographing, and a steady wind, estimated at about 

 11 miles an hour, was blowing in the direction indicated by the 

 arrows in the photographic record of flight. The dusting plane 

 traveled at the rate of 80 miles and hour, and as shown by the 

 photographs, flew along the windward side and parallel to the grove 

 rather than over the trees. Six flights were made past the grove, 

 the plane taking the same path for each passage, which was about 

 53 yards to the windward. The altitude varied from 20 to 35 feet. 



The poison trail was controlled for a few seconds after leaving 

 the plane by the impetus of the "slip stream", but this was soon 

 lost, and the steadily moving wind grasped the poison cloud and 

 carried it, as a wartime barrage, toward the caterpillar-infested 

 grove. When the dust reached the grove, a new influence or force 

 was observed to be at work, for it was noted that air currents were 

 rising from among the trees and the influence of these rising cur- 

 rents, combined with the steady push of the wind was sufficient to 

 carry the poison cloud to all parts of the grove, and even beyond, 

 since some dust settled in a corn field as much as 500 feet to the 

 leeward of the last row of trees. 



Each flight past the grove required 9 seconds and, since six 

 flights in all were made, the total time consumed in the act of 

 liberating the dust was 54 seconds. To have done the same 

 amount of work with a liquid sprayer would have required many 

 hours. 



The total amount of lead used was 175 pounds. In all prob- 

 ability this was more than was actually necessary. 



After the final passage of the plane, a critical examination of 

 the foliage in all parts of the grove was made. Not a catalpa leaf 

 could be found anywhere which did not bear particles of arsenate of 

 lead in sufficient quantity to constitute a killing dose. 



The most gratifying phase of the act of applying the dust was 

 the excellent distribution obtained and the remarkable manner in 

 which it could be controlled and thus deposited where intended. 

 By correlating altitude, wind currents, etc., the behavior of the 



