its place by the framing shouldering
up more than was expected. As a plumb line cannot be used, recourse must be
had to a square; and it will signify nothing at what angle with the deck
the keelsons run, so long as the line of the shaft across the keelsons is
square down from the shaft centre. The sole plates being fixed, there is no
difficulty in setting the other parts of the engine in their proper places
upon them. The paddle wheels must be hung from the top of the paddle box to
enable the shaft to be rove through them, and the cross stays between the
engines should be fixed in when the vessel is afloat. To try whether the
shafts are in a line, turn the paddle wheels, and try if the distance
between the cranks is the same at the upper and under, and the two
horizontal centres; if not, move the end of the paddle shaft up or down,
backward or forward, until the distance between the cranks at all the four
centres is the same.

490. _Q._--In what manner are the engines of a steam vessel secured to the
hull?

_A._--The engines of a steamer are secured to the hull by means of bolts
called holding down bolts, and in wooden vessels a good deal of trouble is
caused by these bolts, which are generally made of iron. Sometimes they go
through the bottom of the ship, and at other times they merely go through
the keelson,--a recess being made in the floor or timbers to admit of the
introduction of a nut. The iron, however, wears rapidly away in both cases,
even though the bolts are tinned; and it has been found the preferable
method to make such of the bolts as pass through the bottom, or enter the
bilge, of Muntz's metal, or of copper. In a side lever engine, four Muntz's
metal bolts may be put through the bottom at the crank end of the framing
of each engine, four more at the main centre, and four more at the
cylinder, making twelve through bolts to each engine; and it is more
convenient to make these bolts with a nut at each end, as in that case the
bolts may be dropped down from the inside, and the necessity is obviated of
putting the vessel on very high blocks in the dock, in order to give room
to put the bolts up from the bottom. The remainder of the holding down
bolts may be of iron, and may, by means of a square neck, be screwed into
the timber of the keelsons as wood screws--the upper part being furnished
with a nut which may be screwed down upon the sole plate, so soon as the
wood screw portion is in its place. If the cy