408 
STEPHENSON’S PATENT 
requiring therefore a construction affording the means of generating steam very 
rapidly, or having a great evaporating power, in order to supply the steam in 
sufficient quantity and of the required pressure. The whole engine has to be very 
strongly and firmly made and framed together, to enable it to resist the violent strains 
and shocks produced by the rapid motion of so heavy a mass even upon the com 
paratively smooth surface of the rails, and also to meet the accidents to which it is 
liable, and which are generally very serious. 
The construction of these engines has undergone very great and extensive improve 
ment during the last few years, and they have not long arrived at their present 
state of perfection ; those made before the last ten years were greatly inferior, having 
not more than a fourteenth of the power of the present ones. 
The engine here described, and shewn in the engravings, contains the latest 
improvements, and is similar in construction to most of those used on railways in 
England and on the Continent. 
DESCRIPTION OF THE ENGINE. 
Plate LXXXIX. is a side elevation of the engine and tender. The engraving is 
highly shaded to show more fully their general appearance. 
Plate XC. a longitudinal section through the centre of the engine and tender, 
showing their internal construction; the section below the boiler being taken through 
the right hand cylinder and crank. 
Plate XCI. Fig. 1, is a plan of the engine and tender; the plan of the engine is 
taken just below the boiler, in order to show the machinery beneath it, and at the 
left cylinder the plan is taken a little lower down, showing a section of the steam 
chest and more of the machinery; figs. 2, 3, and 4 are detached views of the 
working gear for the slide valves; figs. 2 and 3 being side elevations, showing the 
working gear in different positions, to explain their action ; and fig. 4 a back eleva 
tion, showing it in the same position as figs. 1 and 3. The plan of the tender is 
taken at the top. 
Plate XCII. contains an elevation of each end of the engine, and a cross section 
through each of the end portions. 
The plates are all drawn to a scale of three quarters of an inch to a foot, or one- 
sixteenth of the real size, and the same letters of reference are used to denote the 
same parts in each of the figures. 
The different parts of the engine are shown in detail on a larger scale in the wood 
cuts accompanying the descriptions, according to the size or importance of the parts. 
The construction and object of the different parts of the engine will be explained 
in succession, together with the wear to which they are subject, the improve-