of determining the Surface- Tension of Liquids. 595 



Difference of level between the vertices 



= 44*37 divisions or the microscope scale ; 

 = 0-2826 cm. 



Difference 

 of level. 



X. 



2y. 



V 2 

 •2x' 



44;37 

 divisions. 



3-00 

 400 

 500 



600 



45-80 

 52-78 

 58-92 

 64-71 



87-06 

 87-05 

 86-79 

 87-24 



Mean 



8703 



r 



From this it appears that for this plate -^ is very nearly 

 indeed a constant = 87*03 divisions. 



Of course, the edge of the shadow was not a sharp line but 

 a series of very narrow diffraction-fringes. In measuring 

 the difference of level, the position of the geometrical edge of 

 the shadow (G in fig. 3) was estimated and used. But in 

 making the measurement of curvature, a better-defined point 

 (B in^fig. 3) in the curve of illumination was used. 



Fin-. 3. 



GB was carefully measured and found to be 1'16 divisions. 



p = 87-03-1-16 = 85-87 divisions. 



K, by measurement (in a similar fashion) was found to be 

 3400 divisions. 



