engines the boilers also supply it to a variety of auxiliary pumps,
as boiler-feed, fire-pump, blow-off, tank-pump and pump for forcing
water through the building.

The heating arrangement of such a vast area as is covered by the floor
space of a sky-scraper has been a very difficult problem but it has
been solved so that the occupant of the twentieth story can receive
an equal degree of heat with the one on the ground floor. Both hot
water and steam are utilized. Hot water heating, however, is preferable
to steam, as it gives a much steadier heat. The radiators arc
proportioned to give an average temperature of 65 degrees F. in each
room during the winter months. There are automatic regulating devices
attached to the radiators, so if the temperature rises above or falls
below a certain point the steam or hot water is automatically turned
on or off. Some buildings are heated by the exhaust steam from the
engines but most have boilers solely for the purpose.

The sanitary system is another important feature. The supplying of
water for wash-stands, the dispositions of wastes and the flushing of
lavatories tax all the skill of the mechanical engineer. Several of
these mighty buildings call for upwards of a thousand lavatories.

In considering the sky-scraper we should not forget the role played
by the electric elevator. Without it these buildings would be
practically useless, as far as the upper stories are concerned. The
labor of stair climbing would leave them untenanted. No one would be
willing to climb ten, twenty or thirty flights and tackle a day's work
after the exertion of doing so. To climb to the fiftieth story in such
a manner would be well-nigh impossible or only possible by relays, and
after one would arrive at the top he would be so physically exhausted