— 190 — 
growth time so materially influenced the drop-size. The lip 
of a bottle from which a drop falls is usually annuloid. The 
amount of solid in contact with the dropping liquid is deter- 
mined by the size of two diameters ; one measuring the width 
of the rim of the neck, the other the thickness of that rim. 
In most cases the curvature and massing of the solid at the 
point whence the liquid drops, is so irregular as not to admit 
of any mathematical expression. 
The reason why drops which fall from surfaces of greater 
curvature arc larger than those which fall from surfaces of 
lesser curvature is surely this : In the case of a surface of 
greater curvature the base of the drop has more nearly its 
maximum size ; the neighbouring liquid film, from which the 
drop hangs, is, on the whole, nearer to the centre of gravity 
of the hanging drop; .the contact between the two is more ex- 
tensive and intimate so that the drop is held for a longer time 
and therefore grows more. On comparing columns 3 and 5 
of Table IX there does not appear to be any obvious law of 
connexion between the two ; nor indeed can the numbers of 
column 4 pretend to such a degree of accuracy as would jus- 
tify us in attempting to establish one. This is seen on com- 
paring inter se the numbers of column 4. Especially with the 
spheres of longer radii there is so much difficulty in getting 
an uniform wetting of the surface whence the drop falls, and 
this so materially influences the drop-size, that the mimbers 
found are seen to vary considerably. Greater accord is ob- 
tained with spheres of less radii. As we might have expect- 
ed, the same absolute increase in length of radius, takes less 
effect upon the drop size in the case of longer than in that of 
shorter radii. The infinite, or at least indefinitely great dif- 
ference between the radii 1 and 2 produces about the sarre 
effect upon the drop-size as the difference of 43 mm - between 
the radii 2 and 3, and so on. The following table of first dif- 
ferences shows this more strikingly : 
