4OS ON CAPILLARY TUBES AND SIPHONS. 



This however was not very satisfactory ; for what reason is there 

 to think that the air, the particles of which are so minute, will not 

 be at perfect freedom in a tube half a line, or a quarter of a line, 

 in diameter 1 



But whether this explanation be satisfactory or not, it is entirely 

 overturned by the second and third phenomena of capillary tubes. 



2. When mercurv is employed, instead of water, this fluid, in- 

 stead of rising in the capillary branch, to the level which it reaches 

 in the other, remains below that level. 



3. If the experiment be performed in vacuo, every thing takes 

 place the same as in the open air. The cause of this phenomenon 

 then is not to be sought for in the air. 



4. If the inside of the tube be rubbed with any greasy matter 

 such as tallow, the water, instead of rising above I he level, remains 

 below it. The case is the same, if the experiment be made with a 

 tube of wax, or the quills of a bird, the inside of which is always 

 greasy. 



5. If the end of a capillary tube be immersed in watu, this fluid 

 immediately rises above the level of that in the vessel, and to the 

 same height to which it would rise in a syphon, if one of its branches 

 were a capillary tube, and the other of the common size ; so that 

 if the surface of the water only be touched, it is immediately at- 

 tracted, as it were, to the height abovementioned, and it remains 

 suspended at that height when the tube is removed from the 

 water. 



6. If a capillary tube be held in a perpendicular direction, or 

 nearly so, and if a drop of water be made to run along its exterior 

 surface, when the drop reaches its lower aperture, it enters the 

 tube, if it be of sufficient size, and rises to the height at which it 

 would stand, above the level, in the branch of a syphon of that 

 calibre. 



7. The heights at which water maintains itself in capillary tubes, 

 are in the inverse ratio of the diameter. Thus, if water rise to 

 the height of 10 lines in a tube one.third of a line in diameter, it 

 ought to rise to the height of 20 lines in a tube one-sixth of a line 

 in diameter, and to the height of 100 in a tube one.SOth of a line 

 in diameter. 



The falling of mercury below the level in such tubes, follows also 

 the inverse ratio of the diameters of the tubes, 



