339 
Steam Engine. 
rnay both be inclined towards it, as one of them is from 
so as to join the cylinder A near the middle ; or any 
other direction may be given to them, to prevent derange- 
ment by expansion* 
The tubes C and a are kept from separating by bolts 
from the inside of a passing through the top of C, where 
they are secured by nuts screwed on to them (see fig. 5.) ; 
and these parts of C are so contrived, that by taking off 
any of the nuts a cover may be removed, and a hole pre- 
sented large enough to admit a man’s hand into C to clean 
it out. 
Fig, 5 is a longitudinal vertical section of the boiler and 
furnace, through the centre of the axis of the main cylin- 
der A, showing the course which the flame and heated 
air are forced to take. The first three small cylinders are 
completely surrounded with flame, being directly over 
the fire : the flame is stopped by the brick-work W over 
the fifth, and forced to pass under it, and then over the 
sixths where it again meets with an interruption, which 
forces it to go under the seventh, over the eighth, and 
partly over partly under the ninth. It then turns round 
the end of the longitudinal wall which divides the furnace, 
and passes over the eighth smaller cylinder, under the se- 
venth, and so on alternately over and under the other 
tubes, till it reaches the chimney B, fig. 4. The wall 
that divides the furnace may be seen in fig. 3, N,N, and 
in fig. 6, at N. 
To secure a free communication between tlie different 
parts of the boiler, the three tubes of the middle cylinder 
C are connected with those of the two exterior C’s by two 
pipes 0 0 . The other ends of the tubes aa a are each fit 
ted with a cover properly secured and bolted, but which 
can be taken off occasionally to clean out the boiler. 
In working with such boilers, the water carried off I n 
e.Vaporation is replaced by rvater forced in by tlie usual 
