276 Wisconsin Academy of Sciences , Arts and Letters. 
various considerations, it appears that it must exceed the range 
of molecular attraction determined by Quincke, which he 
found to be 20 ten-thousandths of a millimeter. 
When a long, wide glass tube, filled with water and held in 
a vertical position, is at once opened at both ends, permitting 
the water to fail bodily out, there remains behind, at the in¬ 
stant the mass has escaped, enough water to represent a fifm 
having a mean thickness of .1 m. m. Even immediately after 
draining has ceased, there may still be retained enough water 
to make a film of a mean thickness of .03 m. m. In such 
cases as this there appears to be no way in which surface ten¬ 
sion can mechanically effect the retention of such water and yet 
the thickness of the film must exceed Quincke’s range of molec¬ 
ular attraction 600 to 2,000-fold. Unless', therefore, there 
is some other cause for the retention of water in such cases we 
are justified in looking upon these as indicating something as 
to both the fact and the magnitude of a sphere of influence. 
Indeed, it appears clear that if such volumes of water as are 
here pointed out can remain stationary against the walls of a 
glass tube while it is being emptied, a similar volume would be 
likely to move through a fluid with a solid in motion. 
In our studies of soil solutions and of the influence of soils 
and sands upon solutions of extremely soluble salts, phenomena 
have been observed which are difficult to explain except on the 
basis that solids immersed in a fluid may retain about or upon 
their surfaces a layer of the fluid which is restrained by them, 
from moving, or is compelled to move with them, in such a 
manner as to become an integral part of a compound system of 
solid and fluid. It has been found, for example, very difficult 
if not quite impossible to completely wash from a clean quartz 
sand so soluble a salt as potassium nitrate. In one case 50 
grams of the dry sand was repeatedly treated with disulphonic 
acid to free it from all traces of nitric acid and of organic 
coloring matter, after which it was charged with a potassium 
nitrate solution which after a time, was drained away and the 
sand dried. Over 50 grams of the sand, so treated and placed 
in a porcelain evaporating dish, was poured 100 c. c. of dis- 
