cutter. Both journals of the connecting rod are furnished with oil cups,
having a small tube in the centre with siphon wicks. The connecting rod is
a thick flat bar, with its edges rounded.

513. _Q._--How is the cranked axle of locomotives constructed?

_A._--The cranked axle of locomotives is always made of wrought iron, with
two cranks forged upon it toward the middle of its length, at a distance
from each other answerable to the distance between the cylinders. Bosses
are made on the axle for the wheels to be keyed upon, and bearings for the
support of the framing. The axle is usually forged in two pieces, which are
afterward welded together. Sometimes the pieces for the cranks are put on
separately, but the cranks so made are liable to give way. In engines with
outside cylinders the axles are made straight-the crank pins being inserted
in the naves of the wheels. The bearings to which the connecting rods are
attached are made with very large fillets in the corners, so as to
strengthen the axle in that part, and to obviate side play in the
connecting rod. In engines which, have been in use for some time, however,
there is generally a good deal of end play in the bearings of the axles
themselves, and this slackness contributes to make the oscillation of the
engine more violent; but this evil may be remedied by making the bearings
spheroidal, whereby end play becomes impossible.

514. _Q._--How are the bearings of the axles arranged?

_A._--The axles bear only against the top of the axle boxes, which are
generally of brass; but a plate extends underneath the bearing, to prevent
sand from being thrown upon it. The upper part of the box in most engines
has a reservoir of oil, which is supplied to the journal by tubes with
siphon wicks. Stephenson uses cast iron axle boxes with brasses, and grease
instead of oil; and the grease is fed upon the journal by the heat of the
bearing melting it, whereby it is made to flow down through a hole in the
brass. Any engines constructed with outside bearings have inside bearings
also, which are supported by longitudinal bars, which serve also in some
cases to support the piston guides; these bearings are sometimes made so as
not to touch the shafts unless they break.

515. _Q._--How are the eccentrics of a locomotive constructed?

_A._--In locomotives the body of the eccentric is of cast iron, in inside
cylinder engines the eccentrics are set on the axle between the cranks, and
th