Manchester Memoirs^ Vol. Ixv. (1921), No. 5 



3 



The cathetometer is not even necessary to measure the amount by 

 which the capillary is immersed in the liquid. If this distance be deter- 

 mined by attaching a needle to the side of the capillary it is only neces- 

 sary to form and to caliper a magnified image of the capillary and needle 

 using a good photographic lens. 



5. The time of the experiment is appreciably shortened. The accurate 

 determination of a surface tension by the ordinary method is a tedious 

 process, and not one to be adventured upon light-heartedly. In our own 

 case we found that, density determinations apart, an experiment involving 

 32 separate readings of the cathetometer, could be completed in about \\ 

 hours. (We usually made 8 determinations of the pressure, and 8 of the 

 distance between the needle-point and the end of the capillary.) With a 

 " naked-eye " manometer, this time could be greatly cut down. 



We now pass on to consider the experimental details ; a diagrammatic 

 sketch of the apparatus is shown below in Fig. 1 : — 



/'S 



Fig. 1. 



The pressure required to force the liquid to the end of the capillary is 

 produced by gently raising or lowering the bottle F by means of a rack 

 and pinion, and the corresponding pressure is read off on the manometer 



