262 



Mr. A. M. Worthington on the [June 15^ 



from them alone the movements of the liquid which gave rise to them, 

 and the probable uselessness of seeking, while ignorant of these move- 

 ments, a quantitative connexion in the case of any given liquid between 

 the size or number of rings of the pattern and the constants at my dis- 

 posal, viz. the height of fall and diameter of the drop. 



I preferred to endeavour, by means of the electric spark, to see the 

 forms through which the drop passed in the act of making its pattern. 

 In this I have been tolerably successful. 



The principle of the method was to make the drop fall in comparative 

 darkness on the plate, and at the moment of incidence itself to break an 

 electrical circuit, by which means a spark was produced in its neighbour- 

 hood sufficiently bright to illuminate the drop and enable it to be seen in 

 the form which it had at that instant ; to see the consecutive stages it 

 was necessary to postpone the appearance of the spark for excessively 

 short but increasing intervals of time after the first contact of the drop. 

 The accompanying sketch of the apparatus will explain the details of the 

 method. 



A B (fig. 1) is a light wand of cedar wood with a forked end ; it is 

 13| millims. long, 1 millim. wide, 4 miUims. deep. The end B bears 

 the glass plate on which the drop falls, the plate being kept in its place 

 by a spring C, as shown in fig. 2. This wand is fixed on a horizontal 



