is generally thought, and probably
with truth, that those sites are most healthful which have their location
on a basis of granite, or other rock-foundation; in such localities there
is usually a considerable slope of the general surface of the ground,
with the result that water rapidly runs off after rains, and consequently
stagnant pools, which might serve as a breeding place for mosquitoes and
bacteria, do not form. Soils through which water easily permeates are
likewise, as a rule, healthy, though this depends in a measure upon
whether or not they contain a very considerable proportion of vegetable
matter. Clay foundations are healthful where there is a considerable
slope to the surface of the ground, but where this does not exist the
soil is damp, owing to its impermeability, and often has stagnant pools
upon its surface. Marls and alluvial soils are not regarded as being
wholesome, but it is not unlikely that their bad reputation is largely
due to the fact that they generally exist in the neighborhood of rivers
and other considerable bodies of water where mosquitoes are numerous.
There are no reasons going to show that cultivated lands are
unhealthy--even where they receive yearly abundant additions of manure.
Where it is necessary to build in damp localities the site should be
thoroughly drained, and the space upon which the house is constructed
should be carefully covered with some impermeable cement.

_Building Materials._--Of all building materials, the one most commonly
employed in America is wood. This arises from the fact that in the past
we have had unlimited quantities of timber from which lumber could be
procured at a price so reasonable that no other material could ordinarily
be considered. That the wooden house has some advantages cannot be
denied; its walls rapidly cool following the torrid days that so commonly
occur during the summer in almost all portions of the United States, and
it is usually well ventilated as a result of the numerous fissures
naturally existing in its structure.

Next to wood, bricks are most commonly used for building purposes, and
have many advantages, among which are their handsome effect, their
stability, and their being poor conductors of heat; the last mentioned is
of considerable importance, since it keeps both heat and frost from
rapidly permeating the interior, and as a consequence houses constructed
of this material are cooler in summer and warmer in winter.

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