538 THE AMERICAN NATURALIST. [Vou. XXXII. 
Hawaiian Islands show some remarkable peculiarities. They are of 
recent origin, are strongly basic in character, being composed largely 
of silicates soluble in acids. The leaching processes, to which they 
have been subjected, has removed in great measure the acidic con- 
stituents. The glacial soils of America, on the other hand, are 
derived from ancient rocks, and are composed largely of silicates 
insoluble in acids. The basic constituents have been largely removed 
by prolonged weathering, and the soils differ markedly from the rocks 
from which they were derived. 
The soils of the Hawaiian Islands are classified by Maxwell, 
according to the climatic conditions under which they originated, . 
„as follows : 
1. Upland Soils: Those formed under low temperatures and large 
rainfall. 
2. Lowland Soils: Those formed under high temperature and 
small rainfall. 
From analysis made on a large number of samples of these soils, 
it appears that those of the first class contain a large per cent of 
organic matter and nitrogen, while the élements of plant food have 
been largely removed by leaching ; and that the soils of the second 
class have a low content of organic matter and nitrogen, and a high 
percentage of plant-food elements in an available state. These dif- 
ferences are due to the fact that the lowland soils receive the surface 
waters from the upland soils. 
In determining the availability of the food supply of the soils, the 
author assumed that the amount removed by cropping added to the 
amount carried away by drainage waters equaled the total available 
supply. From a large number of analyses made of the waters and 
of agricultural products, it was found that the amount of the various 
elements carried away from the soil by the drainage waters equaled 
the amount of similar elements removed by cropping. By a series of 
experiments to ascertain the action of organic acids of various degrees 
of concentration on the different soil constituents, it was found that 
aspartic acid dissolved the essential plant-food materials in approxi- 
mately the same proportions as they were found in the drainage 
waters. Furthermore, it was found that a one-per-cent solution of 
this acid removed the same amounts of these materials in twenty-four 
hours as ten crops of sugar cane; hence it was concluded that one- 
tenth of the amount of lime, phosphoric acid, and potash removed 
from a soil by a one-per-cent solution of aspartic acid in twenty-four 
hours is the available supply of that particular soil. 
