284 Wisconsin Academy of Sciences, Arts and Letters . 
meter. In the data we have presented indicating the thickness 
of the retained water layer on solids the mean value is .05 mil¬ 
limeter. Taking the thickness of the investing film at one- 
fifth of this, or .01 millimeter, for a clay particle having a diam¬ 
eter of .001 millimeter, its effective diameter would become 
.01 + .001 + .01 = .021 millimeter. 
The effective volume, therefore, in consequence of the investing 
layer of water, would be increased 9,261-fold. Its head resis¬ 
tance to motion would be increased by the square of the effective 
diameter, or 441 times, while the specific gravity would be re¬ 
duced to 1.0002, computed from the formula: 
Sp. Gr. = 
it d s 
, / it D 
6 ^ V 6 
D 3 
6 
it_df\ 
6 ) 
d = diameter of solid nucleus taken as unity. 
D = diameter of solid-fluid system, 
sp. gr. — specific gravity of the nucleus. 
Sp. Gr. = specific gravity of the solid-fluid system. 
We have just stated that the Mississippi delivers to the Gulf 
11 tons of sediment per second. Since the effective specific 
gravity, according to the computation, is only .0002 greater than 
that of the water itself, the vertical component of the force of 
suspension need not exceed 4.4 lbs. in the aggregate for the 
whole section of the stream bearing the 11 tons of sediment. 
And since the increased diameter of the grain, due to the ad¬ 
hering film, augments the effective cross-section of the grain 
441-fold it is clear that a much small vertical motion of the 
water of the stream would be required to maintain suspension 
than if this force were to be exerted upon the surface of the 
grain itself. 
If the same principle is applied to the suspension of dust 
particles in the air and a similar computation made results 
like the following appear: taking the diameter of a dust par¬ 
ticle at .001 millimeter and with a specific gravity of 2.65. 
Taking the ratio of water to air at 62° F. at 1 to 816.8., 
Taking the thickness of the retained air film at .01 millimeter,, 
