
ie 


ECONOMIC ASPECTS OF GEOLOGICAL STRUCTURE 367 
solution, or, on the other hand, there may be an insufficient 
quantity of mineral ingredients present, as in the case of 
water derived from melting snow or ice. Other districts may 
be unhealthy owing to the undrained character of the land. 
It is matter of common knowledge that damp, cold soils 
favour many diseases. Even in one and the same district, 
we may note that houses built on dry rock are healthier 
residences than others in their proximity which are founded 
on damp ground. Once more, the topographical conditions 
of a district necessarily influence the climate and affect the 
health of a community. It has been found, for example, that 
a high rate of mortality prevails in districts which are exposed 
to the full force of the winds sweeping inland from the sea, 
the mortality being largely due to phthisis. 
If, therefore, it be ascertained that the occupants of some 
particular geological area are more subject to certain diseases 
than the denizens of another where the prevailing rocks are 
of a different kind, we need not credit the rocks themselves 
with having any direct influence on the life of man. In 
most cases it will be found that districts are unhealthy either 
because of insufficient drainage, or the water-supply will be 
to blame, or it may be that the topographical conditions do 
not afford sufficient protection from the full force of the 
wind. 
