Sept. 17, 1917 Disease Dissemination by Wind and Rain 



643 



out doubt all are cleaved from the surface film at the same time, and 

 all leave the point of impact with the same energy. The only explana- 

 tion for the presence of the larger drops at the greater distances must 

 lie in the difference in resistance offered by the atmosphere, since the 

 smaller drops would experience greater relative resistance than the 

 larger ones. 



SPLASH FROM A HORIZONTAL SURFACE AT THE LEVEL OF THE 



COUNTER 



The greatest distance of splash results from the fall of the largest drop 

 onto the thin film of water afforded by the wet blotting paper when 

 falling 12 inches. Other things being equal, the distance of splash 

 varies as the size of the drop varies, though not in direct proportion. 

 With drops of each size, respectively, the distance of splash is greater 

 from the wet glass plate than from the water in the petri dish. 



The same relation exists in all the tests made with the drops falling 

 24 and 48 inches, with the exception in the latter case, where the distances 

 from blotting paper and the glass plate were equal in two instances. 

 With the tests made at greater heights, 8 and 16 feet, the thick layer of 

 water in the petri dish was eliminated, since such a factor has no place 

 in the application of the work to field conditions and since the relation 

 of a deep layer of water to the other layers used had been satisfactorily 

 established. 



The figures given in Table II represent the extremes of splash in inches 

 under each of the various sets of conditions and in general show the 

 relation between size of drops, distance of fall, and thickness of surface 

 film in the determination of this distance. The mean distance of all 

 the splash drops farther than 6 inches resulting from the i-, 2-, and 4- 

 foot falls and the average of the extremes of each of 50 single drops fall- 

 ing 8 and 16 feet present the same relation of factors. 



TabIvE II- — Distance (in inchei) of splashes, giving the maxinuini, mean, and average of 



the maximums in 50 trials 



Size of 

 drop. 



Surface of impact. 



Mean. 



Average of 

 maximums. 



Distance of fall .... feet 



C.c. 

 o. I 



{Blotting paper 

 Glass plate 

 Petri dish 



{Blotting paper 

 Glass plate . . . . 

 Petri dish 



[Blotting paper 

 < Glass plate. . . . 



I Petri dish 



(Blotting paper 

 \ Glass plate . . . . 

 (Petri dish 



18. 1 



15-5 

 13- 1 

 15-3 

 12.8 

 II. 4 



13-2 



9-S 

 9-3 

 12.8 

 9.9 



20.8 

 17-8 

 14. I 

 18.4 

 17 o 

 13-4 

 IS- 9 

 14.8 

 II. I 

 14.9 

 II. 6 

 9-S 



