Sept. 17, 1917 Disease Dissemination by Wind and Rain 



641 



composing the surface film at the point of impact. Perhaps in some 

 cases water of the fallen drop is scattered, but the greater part of it 

 remains as a part of the surface film and is splashed by succeeding drops. 



NUMBER AND DISTRIBUTION OF SPLASH DROPS 



While it was a relatively simple process to find the distances of those 

 splash drops scattered farthest over a quadrant of a circle on the counter 

 which was used, it was difficult to obtain an accurate count of the total 

 number of splash drops in this way. In every instance many of the 

 smaller drops, varying from a sixteenth of an inch in diameter to zero, 

 evaporated before the count could be completed. Finally, to determine 

 this point, the acetic-acid and litmus-paper method was resorted to. 

 Five 0.02-c. c. drops falling 16 feet upon a glass plate covered with a 

 solution of acetic acid scattered 495 drops over an eighth of a circle 

 between 2 and 24 inches from the point of impact. When calculated, 

 these figures show that each drop of that size falling that distance broke 

 ofif and scattered 795 drops over a circle with a 24-inch radius. 



The distribution of these splash drops is given in Table I, and it will 

 be noticed that the modal class or distance is between 4 and 6 inches; 

 yet the mean distance when determined is 7.1 inches. 



Table I. — Number of splash drops in concentric circles of varying radii, with the deter- 

 mination of the m£an distance of all the drops 



A reproduction of the distribution of these drops is given in figure i, 

 showing the relative distances and orientation more satisfactorily than 

 that of the foregoing table. A fact prominent in this phase of the work 

 is the presence of the larger splash drops at the extreme distances. 

 The smaller ones are more abundant near the point of impact. With- 



