MOSSOTTI ON CAPILLARY PHA. NOMENA, 565 
the latest notions which we have already expounded on the real 
structure of fluids, I shall attempt to explain the capillary phe- 
nomena with the ingenious ideas set forth by Dr. Young. 
2. The capillary phenomenon which can most easily be ob- 
served, is produced by immersing in a fluid a slender tube of 
small diameter (from about -5™™ to 3™™). If the liquid be such 
as to wet the sides of the tube, the small column of fluid will be 
seen to assume a concave shape at its upper surface and to rise 
toa greater height than the liquid outside the tube; whereas if 
the liquid be of a kind that will not adhere to the sides, the small 
internal column will assume a convex shape at the upper surface, 
and will stand at a lower height. Comparing the elevations or 
_ the depressions of the small columns of fluids in tubes of dif- 
ferent diameters, we find that they vary approximately in the 
inverse ratio of the diameters of the tubes employed. It is from 
the minuteness of the diameters of these tubes, which may be 
_ compared to a hair, that these and other phenomena depending 
_ on the same causes have been called capillary phenomena. 
_ It is not necessary that the fluid that rises above or is de- 
_ pressed below the level of the external portion should be entirely 
enclosed as by the sides of a tube. If we immerse two planes 
at a small distance from one another, the liquid will be seen to 
rise or be depressed between them; but in this case the eleva- 
_ tions or depressions are only about half the amount of those 
produced by a tube of a diameter equal to the distance between 
the two planes. 
_ 3. It would appear at first sight that these elevations or de- 
pressions were an exception to the general principles of hydro- 
statics which we have explained, and according to which a liquid 
ought to rise to the same level in all communicating vessels ; 
but in giving that demonstration we did not consider a peculiar 
circumstance, which did not concern us then, but which, if 
now taken into account, will show us clearly that these varia- 
tions of level, instead of being an exception, are a direct conse- 
quence of the principles according to which we have character- 
ized the molecular forces, which have led us to discover the 
transmission of equal pressure in every direction. (Vide note 1, 
p- 575.) 
We then showed, that if we suppose a plane passing through 
the liquid mass, and upon this plane a small fluid prism perpen- 
