Jackson — A Neio Method of Producing Tension in Liquids. 107 



that due to vapour of the liquid, with, perhaps, a small additional 

 pressure due to evolved air. 



The apparatus employed was simple ; it consisted of a glass 

 tube about -^ in. internal diameter, constricted at the middle to 

 about 2V in. internal diameter. On both sides of the constricted 

 portion smaller tubes were joined in. These tubes, turned up- 

 wards and closed at their upper ends, served as compressed air 

 manometers, readings being taken on a scale fixed behind them. 

 The glass tube was firmly fixed in a wooden base, and at one end 

 it was connected by a short rubber tube capable of standing con- 



Fig. 2. 



siderable pressure to a brass union which afforded easy means of 

 connection with the water pipes in the laboratory. Another short 

 rubber tube connected the other end of the glass tube to a simple 

 form of current meter, the construction of which will be at 

 once evident from the figure (see fig. 2). This form of current 

 meter proved very satisfactory : it adjusted itself very quickly to 

 variations in the current — a point which was of considerable 

 importance, as will be seen later on. 



On connecting the union to a water-tap, and gradually opening 

 the tap, the following observations were made : — 



1st. Pressure-difference, as shown by manometers, and rate of 



