8 Scientific Proceedingfi, Royal Dublin Society. 



that the sprayer working at the same pressure produces a degree of pulverization 

 depending on the purity of the water, the purer water being broken into smaller 

 drops. It may be remarked that the output of the sprayer (as expressed in the 

 dotted curve of fig. 1) is the same for all samples of water. The graphs of fig. 3 

 have been drawn as intersecting straight lines. It is possible that more accurate 

 observation might reveal them as rounded in the region of inflexion. The bending 

 over of the curve may really occur at slightly different pressures for the different 

 samples of water. The pressure at which the change occurs is certainly well 

 removed from the pressures 16, 19, and 21 cm. Hg. at which discontinuities 

 occurred in the curves showing the charge per c.c. plotted against pressure 



(fig- 2). 



The first part of the graph, which is common to the three samples of water, 

 does not pass through the origin. It intercepts the vertical axis at a point corre- 

 sponding to a surface of 130 sq. cm. per "c.c. This is easily understood, for we 

 have been plotting the total surface per c.c. of water, whereas what we are really 

 interested in is the area of new water-surface. It would seem that this value of 

 130 represents the surface area per c.c. of the water issuing from the sprayer 

 before it is broken up. If the issuing jet filled the whole orifice, it could be 

 reo-arded as a cylinder, and its original surface per c.c. would be 2/?% r being the 

 radius of the orifice. The value of ''ijr in this case is about 70. N"ow, the true value 

 of the radius of the water-jet is certainly less than that of the orifice, the water 

 being surrounded by an annular air-blast. To assume that the true radius of the 

 water-jet is half that of the orifice would bring the numbers into approximate 

 agreement. It is not unreasonable, then, to suppose that this intercept gives us 

 the original water-surface per c.c. 



Charge consukred as a function of the new area 'prodiwed. 



We can now combine the results of these curves with those in fig. 2 (charge 

 per c.c. against pressure), and, following the practice of the previous paper, plot 

 the charge per c.c. against the area of new surface per c.c. These curves are given 

 in fig. 4. In the previous work the points were found to lie, roughly, round a 

 straight line passing through the origin, showing that the amount of charging was 

 proportional to the area of new surface. In the present more accurate curves 

 there is a rude suggestion of this relationship, especially if the proper origin of 

 co-ordinates is taken (allowance being made for the original surface area of the 

 water). The simple idea of direct proportionality, however, has to be abandoned. 



Three notable points appear from a consideration of these curves. First, the 

 effect of purity of the water on the charge developed is most important for the smaller 

 degrees of pulverization. For example, the purer sample, when broken into drops 

 of a certain comparatively large size, gives a charge of 2 e.s. units per c.c. The other 

 samples, when broken into drops of the same size, give charges of 0'8 and 0"2 e.s. 

 units per c.c. respectively. In the second place, for high degrees of pulveriza- 

 tion it would seem as if the three curves were going to fuse into one, which mea.ns 

 that if the water is broken into small enough drops the charge per c.c. will be the 

 same whatever the purity of the water. The only difference is that (as the curves 

 in fig. 3 show) it is apparently more difficult to break up the impure water. 

 Finally, the discontinuities on the curves for electric charge, which could not be 

 associated with any value of the electric charge, or any value of the s.praying 

 pressure, appear now on all three curves for the same value of surface-area per 

 c.c, that is, for the same average size of drop. It would appear from these curves 



