pointed out. That a greater draft area is possible in
water-tube boilers does not of necessity indicate that proper advantage
of this fact is taken in all boilers of the water-tube class. In the
Babcock & Wilcox boiler, the large draft area taken in connection with
the effective baffling allows the gases to be brought into intimate
contact with all portions of the heating surfaces and renders such
surfaces highly efficient.

In certain designs of water-tube boilers the baffling is such as to
render ineffective certain portions of the heating surface, due to the
tendency of soot and dirt to collect on or behind baffles, in this way
causing the interposition of a layer of non-conducting material between
the hot gases and the heating surfaces.

In Babcock & Wilcox boilers the standard baffle arrangement is such as
to allow the installation of a superheater without in any way altering
the path of the gases from furnace to stack, or requiring a change in
the boiler design. In certain water-tube boilers the baffle arrangement
is such that if a superheater is to be installed a complete change in
the ordinary baffle design is necessary. Frequently to insure
sufficiently hot gas striking the heating surfaces, a portion is
by-passed directly from the furnace to the superheater chamber without
passing over any of the boiler heating surfaces. Any such arrangement
will lead to a decrease in economy and the use of boilers requiring it
should be avoided.

Capacity--Babcock & Wilcox boilers are run successfully in every-day
practice at higher ratings than any other boilers in practical service.
The capacities thus obtainable are due directly to the efficient
circulation already pointed out. Inasmuch as the construction utilizing
headers has a direct bearing in producing such circulation, it is also
connected with the high capacities obtainable with this apparatus.

Where intelligently handled and kept properly cleaned, Babcock & Wilcox
boilers are operated in many plants at from 200 to 225 per cent of their
rated evaporative capacity and it is not unusual for them to be operated
at 300 per cent of such rated capacity during periods of peak load.

Dry Steam--In the list of the requirements of the perfect steam boiler,
the necessity that dry steam be generated has been pointed out. The
Babcock & Wilcox boiler will deliver dry steam under higher capacities
and poorer conditions of feed water than any other boiler now
manufactured. C