19 
the soils at the completion of the experiments. The organic manures 
resist the flow also but when mixed with mineral fertilizers the 
resistance is less. The data taken from daily observations, not in- 
dicated in the table, show that the passage of water in practically 
all the tubes decreased steadily from day to day after the salts 
became diffused throughout the soil and the clay began to swell. 
This applies only to soils Nos. 530 and 573. 
Soil No. 573. — Percolation through this soil was very slow and 
regular. Like capillary activity, salts had very little effect upon it. 
The amount of water passing through the tubes was less on the last 
day of the experiment than on the first day. There is practically no 
clay present in this soil, so that the action of the salts is probably 
upon the organic matter. This soil is the only one in which any salt 
increased the rate of flow. These salts were calcium sulphate, 
sodium carbonate, and superphosphate. Sodium nitrate strongly 
retarded percolation. 
Soil No. Jf.28. — In this instance it was not possible with the equip- 
ment available to maintain a constant head of water, due to the large 
volume which would percolate during the night. All the materials 
used at first decreased the rate of percolation but the daily rate 
increased steadily, for which reason the series was not carried out so 
completely as in the two previous soils. This increase was probably 
due to a washing out of the substances added. The action of sodium 
carbonate and sodium nitrate was very similar and unhke the effects 
in the above organic soil. The organic manures resist percolation 
quite strongly. The calcium and magnesium salts offer the greatest 
resistance, sodium salts next, ammonium salts next, and potash salts 
the least. 
Soil No. 516. — This soil, owing to its mechanical condition and 
low organic content, offers little resistance to percolation of water. 
The effect of adding any agent is to decrease the flow. However, the 
results obtained indicate that some soils are capable of restoring their 
equihbrium, as is shown by the fact that the depression of the first 
day became less as diffusion became more complete. The dibasic 
salts offer less resistance to percolation than the monobasic. 
FLOCCXJLATION. 
The r6le of flocculation in soils is one of considerable importance 
in a study of soils such as occur in these islands. The red clay is a 
type possessing an unusual tenacity and requires judicious handling 
to prevent puddling and to maintain the colloidal clay in the best 
physical condition. Various investigators, recognizing that a solu- 
ble salt wiU bring about the flocculation of the suspended material 
in a turbid liquid, have studied the relation of this to the improve- 
