288 Wisconsin Academy of Sciences, Arts and Letters. 
the lowering of the freezing point of water, which are associated 
with the addition of salts in solution, as well as with changes 
in viscosity and with the nature of colloid solutions. S'o, too 7 
such a structural control of the water would seem to necessi¬ 
tate a change in optical properties and electrical ones as well.. 
If particles immersed in a fluid become the nuclei of spheres 
of that fluid, surface tension also would result. This surface 
tension would he greatest when the diamater of the spheres is 
smallest and would become negligible when the diameter, in 
terms of the nucleus, is very great. According to this view, 
in a saturated solution the number of nuclei is so great and the 
spheres of fluid so small that any further increase in the sur¬ 
face tension, caused by a fall of temperature or the addition of 
more nuclei, would force a number of the spheres to coalesce, 
thus throwing the nuclei together until the aggregate is great 
enough to cause precipitation and to restore sufficient free fluid 
to again reduce surface tension below the intensity which 
causes coalescence. With this conception, when alum or other 
salt is added to a turbid solution these molecules appropriate 
water to themselves, thereby reducing the diameter of the silt- 
water spheres and increasing their effective specific gravity and 
at' the same time their surface tension until a coalscence of both 
salt and alum spheres is forced, producing sufficiently large 
aggregates to cause them to subside. It is a well established 
fact that strong solutions precipitate particles in suspension 
more quickly and more completely than do those more dilute. 
It is also well established that the salt which causes the precip¬ 
itation is itself, to a considerable extent, thrown out of solution, 
even though that salt is one extremely soluble and chemically 
inert under the conditions, like potassium nitrate. This too 
is what would be expected if a coalescence of spheres took place 
and hence, when the turbid water of a stream commingles with 
the salt water of the sea there begins at once a reduction of 
the thickness of water films about the suspended sediment, 
which increases their effective specific gravity and at the same 
time increases the surface tension, causing flocculation, which 
carries to the bottom both the silt and a portion of the salts 
which initiated the flocculation and final precipitation. 
