23 
conditions depend upon the mechanical composition, the organic 
matter present, and the presence or absence of certain soluble sub- 
stances. 
As a means of measuring the effect of salts upon this cohesive 
property of Hawaiian soils, the procedure described by the Bureau of 
Soils was used.^ In this procedure a mechanical shaker having 
a screening apparatus and operated by a motor is used to insure a 
uniform packing of the soil. By means of this apparatus a cup was 
filled with the soil and by means of a penetratmg apparatus the weight 
necessary to cause a steel cone-shaped needle to penetrate a fixed 
depth was determined. While the results so obtained are not directly 
comparable with results obtained by other investigators, due to slight 
differences which may result from the construction of the apparatus, 
they are comparable among themselves. 
In Table X are shown the salts used in the experiments and the 
penetration with varying moisture contents, 1,500 grams of soil 
being used in making the determinations. After each penetration 
water was added, as shown in the table, weU mixed with the soil and 
allowed to stand one hour before repeating the penetration test. Five 
penetrations were made on each cup of soil and the average taken. 
The cup was refilled for further penetrations, repeating these some 
three or more times at each moisture content if there was any undue 
variation. Water was added up to the point at which it was impos- 
sible to work the soil. Salts were added at the rate of 15 grams per 
1,500 grams soil, or 1 per cent of salt. Portions were taken from 
each cup for moisture determination. 
Table X. — Effect of salts on cohesion in soils under various percentages of moisture. 
SOIL NO. 573. 
Check. 
Potassium 
Calcium 
Superphos- 
AmmoTiium 
Sodium 
Sodium 
sulphate. 
oxid. 
phate. 
sulphate. 
nitrate. 
carbonate. 
<D 
a 
<s 
a 
o 
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a 
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fl 
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a 
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o . 
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-1 
11 
5s 
1.1 
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11 
II 
P 
II 
31 
If 
o8 
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o § 
S^ 
o?, 
§ ^ 
o8 
^^ 
o 3 
^^ 
2.^ 
g^ 
^^ 
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(^ 
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s 
Ph 
S 
Ph 
1^ 
Clh 
a 
p^ 
a 
(U 
Perct. 
Gm. 
Perct. 
Gm. 
Perct. 
Gm. 
Perct. 
Gm. 
Perct. 
Gm. 
Perct. 
Gm. 
Perct. 
Gm. 
13.43 
25.25 
27.25 
16.67 
15.61 
26.25 
15.85 
26.35 
15.55 
29.20 
15.43 
28.60 
14.55 
28.55 
16.94 
27.30 
20.65 
28.85 
19.14 
26.25 
17.62 
27.55 
17.60 
30. 15 
17.87 
27.50 
18.05 
29.95 
19.26 
27.35 
23.14 
26.90 
21.94 
25.15 
20.40 
28.8 
21.22 
29.15 
20.54 
27.7 
21.10 
27.40 
21.70 
27.15 
25.11 
25.00 
24.72 
25.20 
22.96 
28.25 
23.02 
26.35 
23.15 
27.05 
23.78 
25.25 
24.07 
27.30 
I 
SOIL NO. 530. 
3.66 
6.78 
9.98 
12.66 
16.40 
19.30 
50 
48.75 
46.25 
49. 30 
51.50 
48.5 
3.90 
7.14 
11.43 
14.84 
16.86 
21.68 
50.0 
46.9 
49.3 
55.2 
52.0 
51 
8.35 
11.61 
14.50 
17.10 
21.60 
51.5 
48.6 
49.7 
52.2 
47.0 
7.47 
10.50 
14.44 
17.42 
19.86 
48.2 
51.75 
53.5 
52.45 
47.45 
7.47 I 50.6 
11.69 I 51.5 
15.02 
17.33 
20.20 
53.45 
49.7 
48.55 
8.56 
12.56 
14.87 
18.00 
20.31 
52.75 
51.5 
49.9 
50.4 
47.95 
7.47 
11.02 
13.88 
16.76 
49.2 
58.75 
61.0 
69.0 
1 U. S. Dept. Agr., Bur. Soils Bui. 50 (1908). 
