7. _Q._--What is the first point of a marine engineer's duty?

_A._--The safe custody of the boiler. He must see that the feed is
maintained, being neither too high nor too low, and that blowing out the
supersalted water is practised sufficiently. The saltness of the water at
every half hour should be entered in the log book, together with the
pressure of steam, number of revolutions of the engine, and any other
particulars which have to be recorded. The economical use of the fuel is
another matter which should receive particular attention. If the coal is
very small, it should be wetted before being put on the fire. Next to the
safety of the boiler, the bearings of the engine are the most important
consideration. These points, indeed, constitute the main parts of the duty
of an engineer, supposing no accident to the machinery to have taken place.

738. _Q._--If the eccentric catches or hoops were disabled, how would you
work the valve?

_A._--If the eccentric catches or hoops break or come off, and the damage
cannot readily be repaired, the valve may be worked by attaching the end of
the starting handle to any convenient part of the other engine, or to some
part in connection with the connecting rod of the same engine. In side
lever engines, with the starting bar hanging from the top of the diagonal
stay, as is a very common arrangement, the valve might be wrought by
leading a rope from the side lever of the other engine through blocks so as
to give a horizontal pull to the hanging starting bar, and the bar could be
brought back by a weight. Another plan would be, to lash a piece of wood to
the cross tail butt of the damaged engine, so as to obtain a sufficient
throw for working the valve, and then to lead a piece of wood or iron, from
a suitable point in the piece of wood attached to the cross tail, to the
starting handle, whereby the valve would receive its proper motion. In
oscillating engines it is easy to give the required motion to the valve, by
deriving it from the oscillation of the cylinder.

739. _Q._--What would you do if a crank pin broke?

_A._--If the crank pin breaks in a paddle vessel with two engines, the
other engine must be made to work one wheel. In a screw vessel the same
course may be pursued, provided the broken crank is not the one through
which the force of the other engine is communicated to the screw. In such a
case the vessel will be as much disabled as if she broke the screw shaft or
scre