relating to the Cohesion of Fluids. 



337 



C E D is a quadrant of 

 a circle fixed in a vertical 

 plane, gi-aduated into de- 

 grees, and having the line 

 C E in a horizontal posi- 

 tion ; A B is a graduated 

 tube filled with liquid, 

 closed at the upper ex- 

 tremity B, and having 

 its lower extremity, A, 

 enlarged to enable the 

 liquid to run out of the 

 tube. The upper end of 

 the tube being placed 

 upon the centre, C, of 

 the quadrant, the read- 

 ing of the degrees on the 



arc corresponding to the lower edge of the tube gives its incli- 

 nation to the horizon. The times of descent of a given column 

 of liquid were then observed for the various angles of inclination 

 of the tube ; and to give a greater pi'ecision to the observations, 

 the times of descent of equal portions of the column were also 

 duly observed. 



Before using the tubes, they were carefully cleaned, so that 

 all portions of their interior surface might become thoroughly 

 wet with the liquid. The presence of any substance calculated 

 to soil the tube, even in the slightest degree, materially intei*- 

 fered with the success of the experiment. Water will remain 

 suspended, at all angles of inclination, in a closed tube not ex- 

 ceeding three-tenths of an inch diameter, when its interior por- 

 tion at A is quite dry or soiled with some unctuous substance ; 

 thus it appears that, with tubes within this limit of diameter, 

 the cohesion of the particles of the water for one another remains 

 unbroken. 



The experiments which I have made with this apparatus, show 

 that the velocity of discharge increases in a high ratio with the 

 section of the tube ; that in tubes of the same section, the velo- 

 city of descent of the column is uniform ; and that for all tubes 

 within the specified limits of diameter, the angle of maximum 

 discharge is constant, or very nearly constant. When the dia- 

 meter of the tube is comparatively large, the cohesion of the 

 j)articles of the fluid for one another is broken by the weight of 

 the central particles ; and then, in this case, the fluid descends 

 in the tube by the direct action of the force of gravity, without 

 being materially affected by the cohesion of the particles of the 

 fluid to the sides of the tube. 



Phil. Mag. S. 4. Vol. 18. No. 121. Nov. 1859. Z 



