410 



STEPHENSON'S PATENT 



FIG. C. 



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 D 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 XCIL, 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 XCIL). The 

 plates are sometimes set out only so as to approach the outer plates within l 

 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 XCIL) ; 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. 



