LOCOMOTIVE ENGINE. 
465 
have not the inner ones; and instead of them a strong iron frame is placed imme 
diately within the wheels, bearing upon the axles, and having the whole engine 
resting upon it; this gives the engine a lighter appearance, as the wheels are quite 
on the outside. But the outside frame adds considerably to the stiffness of the engine, 
and is of great utility in that respect, particularly when the engine gets thrown off 
the line, as happens occasionally; when the outside frame serves materially to 
protect the machinery. It has also an advantage in enabling the engine man to 
have access to any part of the engine whilst it is working, as the wheels and the 
space between them are covered over by the splashers, and can be readily passed over; 
this is very useful, as the working parts frequently require examining and replenish 
ing with oil whilst running. The friction is less when there is no outside frame, as 
there are but two bearings on the cranked axle instead of five; but they have to 
be the full size of the axle, as they are inside the wheels, which much increases the 
friction of each, and renders the whole but little less than in the other plan; the axle 
is also not held so steadily as with the middle inside bearings. 
Whistle.—Z' (Plates LXXXIX., XC., and XCII.,) is a steam whistle used for the 
purpose of giving warning of the approach of the engine when running; the con 
struction of it is shewn to one quarter size, or four times the scale of the engravings, 
in figs. 45 and 46. It is all of 
brass, and the foot, A, is cast 
hollow, with a fianch, />, at the 
bottom to bolt it upon the fire 
box; it has a cock, G, placed in 
it, with the handle D, and screw 
E, to keep it tight, the handle 
projecting out to allow firm hold 
to be taken of it. The cup F, is 
fixed upon the foot A, by screw 
ing the piece G, upon it, and both 
are turned truly at their outer edges, 
leaving a very narrow passage, II, 
four inches diameter, between them all round. The piece G is hollow, having 
holes, IF, in its sides ; and a pillar, K, stands upon its centre, on which is screwed 
the bell L L, the thin edge of which is brought just over the opening I, and half an 
inch above it. When the cock is opened, the steam enters the cup E, through 
the holes H, and rushes out at the narrow slit I, striking the thin edge of the bell E, 
in a similar manner to the action in organ pipes, and producing an exceedingly shrill 
sound ; some holes, M, are made in the top of the bell, to allow the steam to pass 
3 N 
Fig. 45. Fig. 46.