410 
STEPHENSON’S PATENT 
the boiler and corresponding to it; the boiler 
being fastened to it by means of angle iron 
cc, (Plate XC.,) as shown in the section, half 
size, in fig. 6 ; the angle iron ¿4 is bent round 
the boiler at the place of its junction with 
the fire-box, and riveted to the plates B and C 
of the boiler and fire-box. The plates compos 
ing the front and back of the fire-box are bent 
inwards at right angles all round as at dd, (Plate 
XC.,) forming flanches upon which the plates of 
the sides and top are riveted. 
The Internal Fire-Box C C is of similar shape to the external, but flat at the 
top and closed at all sides except the bottom; a clear space of 3^ inches is left 
all round between it and the external fire-box, and on the side next to the boiler 
the space is 4 inches. The internal fire-box is made of copper plates seven-six 
teenths of an inch thick, except the side next the boiler, which is seven-eighths of 
an inch thick, but all of the plate except the circular portion opposite to the boiler 
is beaten down until it is only seven-sixteenths of an inch thick, the same as the 
rest. The roof and sides of the box are formed of one plate, as shown in the section 
fig. 2, Plate XCII., and another plate forms the back, corresponding to that in the 
front next the boiler; the front and back plates are turned inwards at the edges 
like those of the external fire-box, and the other plate fixed to them by three-quarter 
inch copper rivets. The internal fire-box is fastened at the bottom to the 
external, by setting the plates out until they touch the outer plates, and riveting 
them together with copper rivets, as shown at ff (Plates XC. and XCII.). The 
plates are sometimes set out only so as to approach the outer plates within 1^- 
inch, and a copper ring inserted between them, the rivets being put through the 
ring, and the joint thoroughly closed by hammering it up underneath; but it is 
generally found that the joint keeps watertight best when made by setting the 
plates together and riveting them: a double row of rivets is generally used. An 
oval hole, 14 inches wide and 12 inches high, is cut in the back plate of both fire 
boxes for the fire-door gg (Plate XC., and fig. 1, Plate XCII.); the plate of the 
internal fire-box is set out all round it to meet the outer plate, and the two are 
fixed together by a row of copper rivets; a copper ring is sometimes inserted be 
tween the plates here, as well as in the joint at the bottom of the fire-box. The 
fire-door consists of two wrought iron plates connected together by rivets, leaving 
a space of half an inch between them ; this protects the outer plate from the fire, 
and prevents it from getting too hot. 
a XG. o.