146 Prof. A. Anderson and Mr. J. E. Bo wen : Method of 

 corresponding to the refracted and reflected images, 



,7 R -L 



R 



2 V-l' 



y^ + 1 



and R is found without focussing on the meniscus. The 

 position of the meniscus centre may easily be got from the 

 reading of the reflected image by subtracting R/2. The 

 above method was tested by readings with olive oil, the 

 surface of which can generally be f ocussed on, by calculating 

 the position of the surface of the meniscus, and also getting 

 it by direct focussing : the results agreed to a high degree of 

 accuracy, it is obvious that for opaque liquids (e. g. mercury) 

 this reflexion method can be used to find the radius of cur- 

 vature of the centre of the meniscus provided the surface 

 can be accurately focussed on. 



The following tables give a series of readings with tubes 

 of different diameters for olive oil and mercury. As the 

 surface-tension of mercury varies considerably, freshly distilled 

 mercury was not used, but clean mercury which was filtered 

 through a pin-hole in a paper funnel before each reading. 

 This was clone as we wished to keep the mercury in as far as 

 possible the same condition in order to test the method of 

 finding angles of contact, mercury being the only liquid 

 whose angle of contact is known to any degree of accuracy. 

 The readings with the narrower tubes in the case of mercury 

 could not be taken exactly as described owing to the meniscus 

 being so far below the surface in the vessel, so with these a 

 piece of the tube was sealed to a wide-mouthed funnel and 

 then bent in U-shape until the end of the tube was slightly 

 below the top of the funnel : the readings were then easily 

 taken, r, R, and 7i are given in cm., T in dynes per cm. 



Olive Oil. 



r. 



E. 



h. 



T. 



•328 



•460 



•155 



32-2 



•222 



•267 



•269 



32-4 



■155 



•162 



•441 



322 



•045 



•045 



1-592 



323 



