310 J. LeOonte—Horizontal Motions of small 
ow, 1 e 
radii of curvature of the meniscuses are not very small. € 
movements of the floating bodies are observed to take place 
when they are more than two centimeters distant. The ques- 
tion of fact to be decided is, do the tensions of the external and 
internal meniscuses change with the alteration of the curvature 
of the united intervening meniscus due to the proximity of the 
partly immersed floating solids? If experiment answers this 
question in the affirmative, then the horizontal components of 
the tensile reaction of the exterior and interior meniscuses be- 
surface-tension of a ioe film is measured. his important 
surface-tension per unit of contour, for the numerical values of 
these two quantities are equal.” Hence in the ease of a ies 
surface in contact with the surface of a solid, the whole su 
tension at the line of contact of the liquid film is equal to 4X — 
length of contour in unit lengths. 
Assuming the constancy of the angle of contact and the 
constancy of the surface-tension (T), it is easy to deduce Ju- 
rin’s law for the elevation or depression of liquids in tubes ane 
between parallel plates; and conversely, to find the numerical — 
value of T, the assumed constant of surface-tension. Thus !et 
d = diameter of vertical tube, 
and d'= distance between vertical parallel plates. | 
T = tension per unit-length of contour, for tubes, a 
and 'T’ = tension per unit-length of contour, for paral 
plates. : 
@ = angle of contact (constant), for tubes, : 
and @ = angle of contact (constant), for parallel plates, : 
* “Encyc, Britannica,” Ninth Ed., Article, “ Capillary Action.” 
