Composition of the soil particles — Continued. 
MAGNESIA CONTENT. 
Soil particles. 
Clay 
Fine silt — 
Silt 
Fine sand. . 
Coarse sand. 
Soil 
No. 164. 
Per cent. 
0.76 
2.74 
2.05 
2.65 
Soil 
No. 291 
Per cent. 
0.99 
2.14 
1.59 
2.27 
2.35 
Soil 
No. 292. 
Per cent 
1.18 
2.73 
3.27 
2.27 
23.49 
Soil 
No. 339. 
Per cent. 
1.27 
.96 
1.04 
1.26 
3.22 
Soil 
No. 392. 
Per cent. Per cent 
Soil 
No. 428. 
0.85 
1.22 
.95 
1.59 
1.57 
1.67 
5.98 
4.95 
9.18 
10.38 
Soil 
No. 448. 
Soil Soil 
No. 471. No. 547. 
Per cent. P<r a nt. 
0.71 
1.49 
1.21 
3.44 
15.90 
1.02 
1.42 
2.08 
3.11 
5.13 
Pit cent. 
0.92 
1.55 
2.84 
3.59 
3.03 
Silica. — Generally silica is present in larger amounts in the smaller 
soil particles. As a general rule, it may be said that it is highest 
in clay' and decreases with an increase in the size of the soil grains. 
In the above table there are three exceptions to this rule and each 
of the three samples represents a type geologically of far more recent 
formation than the other soils. Furthermore, disintegration is by 
no means complete, and silica being one of the most soluble con- 
stituents of lava, it is probable that these soils will increase in silica 
content as the clay and silt content increases. 
Iron. — This element is present in largest amounts m the silt and 
fine sand particles and in smallest quantities in the clay. The red 
and brown clay silt loam have the highest iron content. This is one 
of the most insoluble constituents of the lava, and its concentration 
in the soil increases on weathering. 
Alumina. — Theoretically, aluminum should be found in largest 
quantities in clay, since pure clay is an aluminum silicate. This 
holds for only 5 of the 9 types of Hawaiian soil analyzed. The 
general tendency is toward a relation similar to that existing be- 
tween silica content and size of soil particle, namely, a decrease in 
alumina content with an increase in size of particles up to coarse 
sand. In the sand grains, the alumina content is very high, in several 
instances being higher than in clay. It is present in largest amounts 
in the clay silts. 
Titanium. — This element, while entirely inert toward plant 
growth, is of considerable importance in Hawaiian soils. It occurs 
mainly in silt and fine sand grains and is least prevalent in clay. 
"When present in abnormal quantities, titanium is invariably asso- 
ciated with a high iron content and better soil texture than that 
of other red clay silts. 
Phosphoric acid. — This is present in largest amount in clay and 
fine silt particles. This fact probably explains the extremely non- 
available condition in which phosphates exist in Hawaiian soils and 
supports the contention in previous publications of this station that 
the nonavailable properties of phosphates in local soils are due in 
