Sept. 17, 1917 Disease Dissemination by Wind and Rain 



645 



Table IV. — Maximum distance (in inches) of the splash of a 0.02-c. c. drop falling 16 

 feet upon level and inclined wet glass plates 



EFFECT OF WIND UPON DISTANCE OF SPLASH 



As mentioned above, the methods of the experiments were altered 

 when wind was introduced into the work. An 18-inch electric fan was 

 standardized with a wind gauge. While running at its greatest speed, the 

 air was moving at the approximate rate of 10 miles per hour, 5 feet from 

 the fan. In the experiments conducted, the fan was placed 5 feet from 

 the surface of the splash, which itself was elevated 3 feet above the floor. 

 Drops were permitted to fall 16 feet onto a clean glass plate which was 

 very slightly inclined, in order that the surface film might be relatively 

 thin. Dilute acetic acid was supplied to the plate near the point of 

 impact by a siphon from a reservoir. In this way the falling drop scat- 

 tered a solution of acetic acid and the wind blew these splash drops at 

 the approximate rate of 10 miles per hour. The velocity of the wind 

 was being constantly retarded by friction with the surrounding quiet 

 air, and in this respect the extreme distance of splash was less than it 

 would have been had the whole air mass been moving at the same rate. 

 Litmus blotters were placed upon the floor at distances of 6, 8, 10, 12, 14, 

 16, and 18 feet from the point of impact in the path of the wind. After 

 an hour's running the blotters at 6 and 8 feet were almost entirely red, 

 those at 10, 12, and 14 feet were well spotted with red, while that at 

 16 feet showed several, and at 18 feet two red spots. Thus, it is evident 

 that water was blown as far as 18 feet under the conditions of this ex- 

 periment. 



It was noted above that the larger splash drops exceeded the distance 

 of the smaller splash drops. This does not obtain when the splash 

 takes place in the wind, since the direction of atmospheric resistance is 

 altered, and the smaller drops are borne farther than the larger, heavier 

 ones. Considering the fact that splash drops vary in size^from % inch 

 in diameter to zero, the smallest ones may be carried correspondingly 

 greater distances than the larger. These, without doubt, evaporated 

 in transit in our experiments because of the dry atmosphere in the lab- 

 oratory. In a humid atmosphere it is possible these may be carried 



