288 Dr. R. A. Lehfeldt on the 



since the rate of flow depends on the fourth power of the 

 radius it is easy to make the tube too wide or too narrow. 

 Of course I made a good many failures at first, but after 

 some practice could rely on getting the required condition. 

 I used tubing of about 1 millim. internal diameter, and 

 4 millim. external, and drew it out till the internal diameter 

 was about one sixth of a millimetre ; a few centimetres of 

 such a bore gives a convenient rate of flow for liquids of the 

 viscosity of water. 



Ficr. 1. 



AT 



D' 



The apparatus for vapour-pressure measurements is shown 

 in fig. 1. It consists of a U-tube, A, to serve as a gauge, 

 carrying a branch, B, below, drawn out for filling as mentioned 

 above. The top of the gauge-tube is bent round each side to 

 the bulbs C, C, which are also provided with filling- tubes 



