The steam engine familiarly explained and illustrated; with an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain maxims for railway speculators. By the Rev. Dionysius Lardner ... With additions and notes by James Renwick ...

LOCOMOTIVE ENGINES ON RAILWAYS. 171
attained by the following admirable arrangement in the
Rocket:This engine is represented in fig. 55. It is supported on
four wheels; the principal part of the weight being thrown
r F 65.
_
on one pair, which are worked by the engine. The boiler
consists of a cylinder six feet in length, with flat ends; the
chimney issues firom one end, and to the other end is attached
a square box, B, the bottom of which is furnished with the
grate on which the fuel is placed. This box is composed of
two casings of iron, one contained within the other, having
between them a space about 3 inches in breadth; the magnitude of the box being 3 feet in length, 2 feet in width, and
3 feet in depth. The casing which surrounds the box communicates with the lower part of the boiler by a pipe marked
c; and the same casing at the top of the box communicates
with the upper part of the boiler by another pipe marked
D. When water is admitted into the boiler, therefore, ip