46 
The Queensland Naturalist 
October, 1929? 
The most immature soils are sometimes called skeletal 
soils, for they are merely the disintegrated portions of the 
underlying rock. Between such Skeletal Soils and those 
mature soils which represent a perfect equilibrium with 
the climate there are a host of soils of many kinds, some 
of which still retain the mineralogical characters of their 
respective rocks, while others already show signs of the 
more important influence wielded by climate. 
The preponderance of the climatic over the geolo- 
gical factor is well seen if one compares a geological map- 
of Europe with a soil map of Europe. The two have not 
the slightest resemblance. The geological map looks like 
a patchwork quilt, the soil map appears as several broad 
bands roughly parallel and concentric with the north 
pole and coinciding almost exactly with well-marked 
climatic regions. 
But, although theoretically any soil should ultimately 
reach equilibrium with its environment, provided it re- 
mains in place for a sufficient length of time, there are 
practically many factors which influence and may retard 
or even inhibit the production of a mature soil. 
Thus temperature has marked effects upon the chemical 
changes involved in the production of soil so that maturity 
would be arrived at more quickly in tropical than in 
temperate regions. And the same may be said of rainfall. 
Topography, too, woulid play an important part for, 
except in those climates of very rapid soil changes, the 
soils of mountainous and hilly country would be washed 
away long before equilibrium with the environment could 
be attained. Another important factor is the chemical re- 
lationship between the original rock and the particular 
soil which should exist to satisfy the climatic conditions. 
Thus a soil rich in iron and alumina would be formed 
more readily from a ferruginous shale than from a quartz- 
ose sandstone. A ferruginous clay in a tropical lowland 
of high rainfall would seem to be an ideal combination of 
conditions for the rapid formation of a mature soil, but if 
even one of the factors (1) Bock composition, (2) Tem- 
perature, (3) Rainfall, (4) Topography, chances to be 
unfavourable the production of a mature soil might be an 
extremely slow process. 
In spite of the many exceptions that these considera- 
tions will entail, the two following rules appear to be the 
only logical conclusions, viz. : 
1. That under any one set of climatic conditions all 
rocks tend to produce the same soil type. 
