high ground-water level
(about five feet from the surface) is unhealthy; and a fluctuating
level, varying from high to low, is the most unhealthy, and is
dangerous to life and health. Many authorities have sought to
demonstrate the intimate relations between a high water level in the
soil and various diseases.

A damp soil, viz., a soil wherein the ground moisture is very great
and persistent, has been found inimical to the health of the
inhabitants, predisposing them to various diseases by the direct
effects of the dampness itself, and by the greater proneness of damp
ground to become contaminated with various pathogenic bacteria and
organisms which may be drawn into the dwellings by the movements of
the ground air. As a rule, there is very little to hinder the ground
air from penetrating the dwellings of man, air being drawn in through
cellars by changes in temperature, and by the artificial heating of
houses.

The organic impurities and bacteria found in the soil are especially
abundant in large cities, and are a cause of the evil influence of
soil upon health. The impurities are allowed to drain into the ground,
to pollute the ground water and the source of water supply, and to
poison the ground air, loading it with bacteria and products of
putrefaction, thus contaminating the air and water so necessary to
life.

=Diseases Due to Soil.=--A great many diseases have been thought to be
due to the influence of the soil. An aetiological relation had been
sought between soil and the following diseases: malaria, paroxysmal
fevers, tuberculosis, neuralgias, cholera, yellow fever, bubonic
plague, typhoid, dysentery, goitre and cretinism, tetanus, anthrax,
malignant Oedema, septicaemia, etc.

=Sites.=--From what we have already learned about the soil, it is
evident that it is a matter of great importance as to where the site
for a human habitation is selected, for upon the proper selection of
the site depend the health, well-being, and longevity of the
inhabitants. The requisite characteristics of a healthy site for
dwellings are: a dry, porous, permeable soil; a low and nonfluctuating
ground-water level, and a soil retaining very little dampness, free
from organic impurities, and the ground water of which is well drained
into distant water courses, while its ground air is uncontaminated by
pathogenic bacteria. Exposure to sunlight, and free circulation of
air, are also requisite.

According to Parkes, the soils in t