540 THE STEAM-ENGINE. 



ing axles and wheels being sufficient for the support of the machine. Con- 

 nected with this change is another, recommended by Mr. Robert Stephenson, 

 by which the flanges are removed from the driving wheels, those upon the 

 remaining pairs of wheels being sufficient to keep the engine in its position upon 

 the rails. We shall now describe a locomotive engine similar in construction 

 to those almost universally used at present on railroads, as well in this as in 

 other countries. 



In fig. 67 is exhibited a vertical section of the engine made by a plane car-, 

 ried through its length ; and in fig. 68, is exhibited a corresponding section of 

 its tender the tender being supposed to be joined on to the engine at the part 

 where the connecting points appear to be broken in the drawing. In fig. 69, 

 is exhibited the plan of the working machinery, including the cylinders, 

 pistons, eccentrics, &c., which are under the boiler, by the operation of which 

 the engine is driven. Fig. 70, represents the tender, also taken in plan. 



In fig. 71, is represented an elevation of the hinder end of the engine next 

 the fire-box ; and in fig. 72, is represented a cross vertical section through the 

 fire-box, and at right angles to the length of the engine, showing the interior 

 of the boiler above and beside the fire-box, the rivets arid bolts connecting 

 the internal and external fire-boxes, the regulator, steam funnel, and steam 

 dome. 



In fig. 73, is represented an elevation of the front of the engine next the 

 smoke-box, showing the cylinder covers W, buffers T, &c. ; and in fig. 74, is 

 represented a section of the interior of the smoke-box, made by a vertical 

 plane at right angles to the engine, showing the tube-plate forming the fore- 

 most end of the boiler, the branches S of the steam-pipe leading to the cylin- 

 ders, the blast-pipe p, the cylinders H, and the chimney G. 



The same letters of reference are placed at corresponding parts in the dif- 

 ferent figures. 



The boiler, as has been explained in the engines already described, is a 

 cylinder placed upon its side, the section of which is exhibited at A, fig. 67. 

 The fire-box consists of two casings of metal, one within the other. The 

 fire-grate is represented at D. The tubes by which the products of combustion 

 are drawn from the fire-box to the smoke-box F are represented at E. Upon 

 the smoke-box is erected the chimney G. In the engine from which this 

 drawing has been taken, and which was used on the London ana 1 Birmingham 

 railway, the boiler is a cylinder, 7\ feet long, and 3J feet in diameter. It is 

 formed of wrought-iron plates -f s of an inch in thickness, overlapping each 

 other, and bound together by iron rivets | of an inch in diameter and If inch 

 apart. One of these rivets, as it joins two plates, is represented in fig. 65. 

 The boiler is clothed with a boarding of wood a, an inch in thickness, and 

 bound round by iron hoops screwed together at the bottom. Wood being a 

 slow conductor of heat, this covering has the effect of keeping the boiler warm, 

 and checking the condensation of steam which would otherwise be produced 

 by the rapid motion of the engine through the cold air. 



The external fire-box, B B, is a casing nearly square in its plan, being four 

 feet wide outside, and three feet seven and a half inches long, measured in 

 the direction of the boiler. It is constructed of wrought-iron plates, similar 

 to those of the boiler. This box descends about two feet below the boiler, 

 the top being semi-cylindrical, as seen in fig. 72, of a somewhat greater diameter 

 than the boiler, and concentrical with it. The front of the fire-box next the 

 end of the boiler has a circular opening equal in size to the end of the boiler. 

 To the edge of this opening the boiler is fastened by angle irons, and rivets 

 in the manner represented in fig. 66. These rivets are seen in section in 

 fig. 67. 



