Scientific Proceedings^ Royal Dublin Society. 



charge per c.c. was fairly constant on different parts of the spray, tending to be 

 somewhat higher towards the edges, where the small drops were more numerous. 

 On the whole, the result of these tests showed tliat the character of the spray did 

 not vary much from point to point, and that it was therefore justifiable to deal 

 with it as a whole for purposes of measurement. 



In order to get an estimate of the degree of pulverization for the whole spray, 

 the following method was adopted : microscope slides, each having a thin layer of 

 oil spread on its surface as already described, were arranged on a long glass plate 

 at intervals of 10 cms. The plate was placed parallel to the long edge of the 

 rectangular receiving vessel, and then drawn across qiiickly, traversing the full 

 width of the vessel. Each of the microscope slides thus received a number of 

 drops corresponding to the vertical section of the cone of spray directly above it. 

 The drops captured on the slides were then measured and counted. In measuring 

 the drops a low-power mici'oscope was used, furnished with a scale in the eye-piece 

 on which sixteen divisions corresponded to 1 mm. The drops were classified as of 

 diameter i, 1, 1|, . . . divisions ; those of diameter between say f and 1\ division 

 being returned as of diameter = 1 division. Very few drops of diameter less than 

 J division were observed. The method of working will be understood from the 

 following table, which gives the results of a " census " of the drops produced from 

 a sample of water at a certain spraying pressure. This table gives the number of 

 drops of each of the standard sizes captured on the microscope slides at different 

 parts of the spray. 'I'he results of a number of observations made under the same 

 conditions are here combined: — 



The question arises as to the proper method of treating these measurements of 

 in order to express the degree of pulverization of the water. In the previous 



