on the Cohesion of Fluids. 77 
far as to determine in many cases the circumstances under 
which a drop of any fluid would detach itself from a given 
surface. But it is sufficient to infer, from the law of the super- 
ficial cohesion of fluids, that the linear dimensions of similar 
drops depending from a horizontal surface must vary pre- 
cisely in the same ratio as the heights of ascent of the respec- 
tive fluids against a vertical surface, or as the square root of 
the heights of ascent in a given tube : hence the magnitudes 
of similar drops of different fluids must vary as the cubes of 
the square roots of the heights of ascent in a tube. I have 
measured the heights of ascent of water and of diluted spirit 
of wine in the same tube, and I found them nearly as 100 to 64 : 
a drop of water falling from a large sphere of glass weighed 
1.8 grains, a drop of the spirit of wine about .85, instead of 
.82, which is nearly the weight that would be inferred from 
the consideration of the heights of ascent, combined with that 
of the specific gravities. We may form a conjecture respecting 
the probable magnitude of a drop by inquiring what must be 
the circumference of the fluid, that would support by its 
cohesion the weight of a hemisphere depending from it : this 
must be the same as that of a tube, in which the fluid would 
rise to the height of one-third of its diameter ; and the square 
of the diameter must be three times as great as the appropriate 
product; or, for water .12; whence the diameter would be 
.35, or a little more than one-third of an inch, and the weight 
of the hemisphere would be 2.8 grains. If more water were 
added internally, the cohesion would be overcome, and the 
drop would no longer be suspended, but it is not easy to cal- 
culate what precise quantity of v/ater would be separated with 
it. The form of a bubble of air rising in water is determined 
