using oil of only what is considered a moderate
price, allowing the engineer in charge to attend to the economical
working of both engines and boilers (as well as many other engines of
all kinds now placed on board a large mail and passenger steamer),
instead of getting many a drenching with sea water, and worried by
close attention to one or two hot bearings all the watch. Compare
these results with the following: In the same service in 1864, and
with no blame to the engineer in charge, the crank shaft bearings of a
screw steamer had to be lined up every five days at intermediate
ports, through insufficient bearing surfaces. Sea water had
continually to be used, resulting in frequent renewal of crank shaft.
Steamers can now run 25,000 miles without having to lift a bearing,
except for examination at the end of the voyage. I would note here
that the form of the bearings on which the shafts work has also been
much improved. They are made more of a _solid character_, the metal
being more equally disposed _round_ the shaft, and the use of gun
metal for the main bearings is now fast disappearing. In large engines
the only metals used are cast iron and white brass, an advantage also
in reducing the amount of wear on the recess by corrosion and grinding
where sea water was used often to a considerable extent.

[Illustration: Fig. 1
Fig. 2]

Figs. No. 1 and No. 2 show the design of the old and new main
bearings, and, I think, require but little explanation. Most of you
present will remember your feelings when, after a hot bearing, the
brasses were found to be cracked at top and bottom, and the trouble
you had afterward to keep these brasses in position. When a smoking
hot bearing occurred, say in the heating of a crank pin, it had the
effect of damaging the material of the shaft more or less, according
to its original soundness, generally at the fillets in the angles of
the cranks. For when the outer surface of the iron got hot, cold
water, often of a low temperature, was suddenly poured on, and the hot
iron, previously expanded, was suddenly contracted, setting up strains
which in my opinion made a small tear transversely where the metal was
_solid_; and where what is termed lamination flaws, due to
construction, existed, these were extended in their natural direction,
and by a repetition of this treatment these flaws became of such a
serious character that the shafts had to be condemned, or actually
gave w