was raised from an initial temperature of the boiler and its
contained water of 72 degrees to a pressure of 200 pounds, in 12-1/2
minutes after lighting the fire. The boiler also responds quickly in
starting from banked fires, especially where forced draft is available.

In Babcock & Wilcox boilers the water is divided into many small streams
which circulate without undue frictional resistance in thin envelopes
passing through the hottest part of the furnace, the steam being carried
rapidly to the disengaging surface. There is no part of the boiler
exposed to the heat of the fire that is not in contact with water
internally, and as a result there is no danger of overheating on
starting up quickly nor can leaks occur from unequal expansion such as
might be the case where an attempt is made to raise steam rapidly in
boilers using water leg construction.

Storage Capacity for Steam and Water--Where sufficient steam and water
capacity are not provided in a boiler, its action will be irregular, the
steam pressure varying over wide limits and the water level being
subject to frequent and rapid fluctuation.

Owing to the small relative weight of steam, water capacity is of
greater importance in this respect than steam space. With a gauge
pressure of 180 pounds per square inch, 8 cubic feet of steam, which is
equivalent to one-half cubic foot of water space, are required to supply
one boiler horse power for one minute and if no heat be supplied to the
boiler during such an interval, the pressure will drop to 150 pounds per
square inch. The volume of steam space, therefore, may be over rated,
but if this be too small, the steam passing off will carry water with it
in the form of spray. Too great a water space results in slow steaming
and waste of fuel in starting up; while too much steam space adds to the
radiating surface and increases the losses from that cause.

That the steam and water space of the Babcock & Wilcox boiler are the
result of numerous experiments has previously been pointed out.

Accessibility--Cleaning. That water-tube boilers are more accessible as
a class than are fire-tube boilers has been indicated. All water-tube
boilers, however, are not equally accessible. In certain designs, due to
the arrangement of baffling used it is practically impossible to remove
all deposits of soot and dirt. Frequently, in order to cheapen the
product, sufficient cleaning and access doors are not supplied as part
of the bo