these are easily confined to narrow limits and readily extinguished
with the apparatus at hand. Steel columns will not burn, but if exposed
to heat of sufficient degree they will warp and bend and probably
collapse, therefore they should be protected by heat resisting agents.
Nothing can be better than terra-cotta and concrete for this purpose.
When terra-cotta blocks are used they should be at least 2 inches thick
with an air space running through them. Columns are also fire-proofed
by wrapping expanded metal or other metal lathing around them and
plastering.

Then a furring system is put on and another layer of metal, lathing
and plastering. This if well done is probably safer than the layer of
hollow tile.

The floor beams should be entirely covered with terra-cotta blocks or
concrete, so that no part of them is left exposed. As most office
trimmings are of wood care should be taken that all electric wires are
well insulated. Faulty installation of dynamos, motors and other
apparatus is frequently the cause of office fires.

The lighting of a sky-scraper is a most elaborate arrangement. Some
of them use as many lights as would well supply a good sized town. The
Singer Building in New York has 15,000 incandescent lamps and it is
safe to say the Metropolitan Life Insurance Building has more than
twice this number as the floor area of the latter is 2-1/2 times as
great. The engines and dynamos are in the basement and so fixed that
their vibrations do not affect the building. As space is always limited
in the basements of sky-scrapers direct connected engines and dynamos
are generally installed instead of belt connected and the boilers
operated under a high steam pressure. Besides delivering steam to the