place, it will
not burn. Neither will granite, but granite will fall to pieces in a
hot fire. Granite is made of quartz, mica, and feldspar, as has been
said before. These three do not expand alike in heat; and therefore
great flakes of the stone split off, so that it really seems to melt
away. A well-made concrete is not affected by fire. It will not burn,
and it will not carry heat to make other things burn. For a concrete
house no paint is needed and less fuel will be required to keep it
warm. If the floors are made with even a very little slant,
"house-cleaning" consists of removing the furniture and turning on the
hose. Water-tank, sink, washtubs, and bathtubs can be cast in concrete
and given a smooth finish. Wooden floors can be laid over the
concrete, or a border of wood can be put around each room for tacking
down carpets or rugs. A concrete house may be as ornamental as the
owner chooses, for columns and cornices and mouldings can easily be
made of concrete; and if they are cast in sand, as iron is, they will
have a finish like sandstone.

It is somewhat troublesome to lay concrete in very cold weather,
because of the danger of freezing and cracking. Sometimes the
materials are heated, and after the concrete is in place, straw or
sand or sawdust is spread over it. These will keep it warm for several
hours, and so give the concrete a chance to "set." Sometimes a canvas
house is built over the work. When a concrete dam was to be built in
the Province of Quebec and the mercury was 20 deg. below zero, the
contractors built a canvas house over one portion of the dam and set
up iron stoves in it. When this part was completed, they took down the
house and built it up again over another portion of the dam.
Sometimes salt is used. Salt water is heavier than fresh water and
will not freeze so easily. Therefore salt put into the water used in
making the concrete will enable it to endure more cold without
freezing; but not more than one pound of salt to twelve gallons of
water should be used.

[Illustration: BUILDING A CONCRETE ROAD

_Courtesy Alpha Portland Cement Co._

The concrete mixer travels along the prepared roadbed, and after it
follow the workmen with levelers and stamps.]

Concrete objects to being frozen before it is "set," but it is
exceedingly accommodating about working under water. It must, of
course, be carried in some way through the water to its proper place
without being washed away, but this i