own in section, and Figure 317 is an end view of the boiler and
setting at the furnace end. The boiler is supported on each side by
channel iron columns, these being riveted to the boiler shell angle
pieces which rest upon the columns. The heat and products of combustion
pass from the furnace along the bottom of the boiler, and at the end
pass into and through the tubes and thence over the top of the boiler
to the chimney flue. There is shown in the bridge wall an opening, and
its service is to admit air to the gases after they have passed the
bridge wall, and thus complete the combustion of such gases as
may have remained unconsumed in the furnace. The cleansing
door at one end and that lined with asbestos at the other, are to admit
the passage of the tube cleaners. The asbestos at the top of the boiler
shell is to protect it from any undue rise in temperature, steam being a
poorer conductor of heat than water, and it being obvious that if one
side of the boiler is hotter than the other it expands more from the
heat and becomes longer, causing the boiler to bend, which strains and
weakens it. The sides of the setting are composed of a double row of
brick walls with an air space of three inches between them, the object
being to prevent as far as possible the radiation of heat from the
walls. The brick-staves are simply stays to hold the brick work together
and prevent its cracking, as it is apt, in the absence of staying, to
do.

[Illustration: Fig. 318. (Page 299.)]

Figures from 318 to 330 are working drawings of a 100-horse engine,
designed also by William H. Hoffman.

Figure 318 represents a plan and a side view of the bed-plate with the
main bearing and the guide bars in place. The cylinder is bolted at the
stuffing box end to the bed-plate, and is supported at the outer end by
an expansion link pivoted to the bed-plate. The main bearing is provided
with a screw for adjusting the height of the bottom piece of the
bearing, and thus taking up the wear. The guide bars are held to the bed
in the middle as well as at each end.

Figures 319 and 320 represent cross sections of the bed-plate.

[Illustration: Fig. 319--CROSS SECTION OF BED PLATE NEAR JUNCTION WITH
CYLINDER. (Page 299.)]

[Illustration: Fig. 320.]

[Illustration: Fig. 321--100 H.P. HORIZONTAL STEAM-ENGINE--ELEVATION OF
CYLINDER--SCALE 1-1/2" = 1 FOOT. (Page 299.)]

[Illustration: Fig. 322--100 H.P. HORIZONTAL STEAM-ENGINE--END VIEW OF
CYLINDER--SCA