| 430 | 43.00
154 | 8 | 8 | 96 | 640 | 65.00
155 | 8 | 10 | 150 | 875 | 85.00
156 | 10 | 8 | 120 | 750 | 73.00
157 | 10 | 10 | 180 | 970 | 95.00
158 | 10 | 12 | 270 | 1400 | 128.00
159 | 12 | 12 | 324 | 1600 | 150.00
=====+========+==========+==========+========+========

There are many combinations and forms of these structures, and a
detailed description of their characteristic construction and cost would
occupy too much space for this present work. By referring to the pages
of any agricultural, architectural, or engineering magazine,
advertisements may be found of firms who build such towers and who may
be depended upon for satisfactory work.

[Illustration: FIG. 52.--Iron tank.]

If the tank is to be placed inside a building, it may be built of steel
or of wood, although a lining of lead, copper, or galvanized iron is of
advantage in the latter case. If the tank is out of doors, protection
against frost must be carefully attended to, both to prevent an ice cap
forming in the tank--the cause of many failures of tanks--and to
prevent standing water in the connecting pipes being frozen. If the tank
is to be placed inside the building, care must be taken to have it
water-tight and to have the supports of the tank ample for the excessive
weight which will be thereby imposed. Wooden tanks are likely to rot,
and if left standing empty, become leaky. They are, therefore, less
worth while than iron tanks.

[Illustration: FIG. 53.--Hand pump applied to air-tank.]

_Pressure tanks._

A simple and very satisfactory method of storing water, and at the same
time making provision for pumping water, is to place in the cellar or in
a special excavation outside the cellar a pressure tank similar in shape
to an ordinary horizontal boiler. The water in this tank is forced up
into the house through the agency of compressed air, pumped in above
the water, either by hand or by machinery, and in some cases
automatically regulated so that the air pressure in the tank remains
constant, no matter whether the tank contains much or little water. The
village supply of Babylon, Long Island, is on this principle, the tanks
there being eight feet in diameter and one hundred feet long,--much
larger, of course, than is needed for a single house.

[Illustration: FIG. 54.--Engine applied to air-tank.]

The accom