The classification of soils has been attempted in a variety of ways, and although it is now generally recognised
that climate probably forms the basis of the broadest classification, yet the geological nature of the parent material is very
important, especially in a country like Britain, where the chief
problem is the subdivision of the climatic types. In Glinka's
scheme of classification (1), which is now widely adopted, soils
are divided into two groups, an ectodynamomorphic or, mature
group, and an endodynamomorphic or, immature group. The influence of the parent material on the soil is still apparent in
this latter group and it is with this group that we have to deal
The method of analysis used by the writer was as follows.
The fine sand fraction got by mechanical analysis of the sol]
was taken and ignited. The minerals present were first separated
into two groups according to specific gravity, the liquid used
being bromoforrl. This gives two groups of-minerals, one of
specific gravity greater than 2.9, the other lower. The first
group is found to contain mainly iron oxides and the ferromagnesian silicates, and the second, quartz, feldspars, and also
flaky minerals like the micas and weathered ferro-magnesian silicates which remain in the lower group by reason of their habit ca lowered density through weathering, though their density when fresh
would put them in the heavy group. The lighter group is then
separated into two fractions, one of specific gravity greater
than 2.6, the other lower. bromoform is diluted with zylol to
a suitable density for the latter separation. Resort is made to
the electromagnet to remove the micas and the weathered ferrouiagnesian silicates from the lighter groups.
The three fractions, one of spedific gravity less than
2.6, the second of specific gravity greater than 2.6 and less than
2.9, and the third of specific gravity greater than 2.9 are, in
theory, characterised by orthoclase, quartz/ plagioclase,and ferromagnesian silicates respectively but in practice it is very difficult to obtain a clean separation of the lighter groups. This
difficulty is caused by the fact that the difference in specific
gravity between orthoclase (2.56) and quartz (2.65) is only 0.09,
while the plagioclases range from 2.62 to 2.75. The presence of
inclusions in such cases also render the separation difficult.
The percentage figure obtained for the heavy group is much more
The "coarse sand" and "silt" fractions of the mechanical
analysis were also examined for comparative purposes, but no
attempt was made to separate the minerals, the silt fraction not
being capable of grading by ordinary gravity separation, owing to
surface tension effects. A separation of the magnetic minerals
can, however, be made by means of the electro-magnet.
The area from which the soils were taken for this study
lies between the hivers Forth and Tweed and comprises the counties
of West Lothian, Midlothian, East Lothian, Berwickshire, Roxburghshire, Selkirkshire and Peebleshire.