hat would result in the construction of a
flue; but it is preferable that they pass directly through the floors,
with the openings protected by automatic hatchways which close
whenever the elevator car is absent. In the washroom, etc., in these
towers, it is desirable to protect the wood floors by means of a thin
layer of asphalt.

BASEMENT FLOORS.

There are difficulties connected with the floors on or near the
ground, by reason of the dry rot incident to such places. Dry rot
consists in the development of fungus growth from spores existing in
the wood, and waiting only the proper conditions for their
germination. The best condition for this germination is the exposure
to a slight degree of warmth and dampness. There have been many
methods of applying antiseptic processes for the preservation of wood;
but, irrespective of their varying degrees of merit, they have not
come into general use on account of their cost, odor, and solubility
in water.

It is necessary that wood should be freely exposed to circulation of
air, in order to preserve it under the ordinary conditions met with in
buildings. Whenever wood is sealed up in any way by paint or varnish,
unless absolutely seasoned, and in a condition not found in heavy
merchantable timber, dry rot is almost sure to ensue. Whitewash is
better.

There has recently been an instance of a very large building in New
York proving unsafe by reason of the dry rot generated in timbers
which have been completely sealed up by application of plaster of
Paris outside of the wire lath and plaster originally adopted as a
protection against fire. Wire lath and plaster is one of the best
methods of protecting timber against fire; and, if the outside is not
sealed by a plaster of stucco or some other impermeable substance, the
mortar will afford sufficient facilities for ventilation to prevent
the deposition of moisture, which will in turn generate dry rot.

Where beams pass into walls, ventilation should be assured by placing
a board each side of the beam while the walls are being built up, and
afterward withdrawing it. In the form of hollow walls referred to, it
is a common practice to run the end of the beam into the flue thus
formed, in order to secure ventilation.

I am well acquainted with a large mill property, one building of which
was erected a short time before the failure of the corporation, which
resulted in the whole plant remaining idle several years. After the
laps