mportance
according to the immense bills they occasion month by month, or the
delays and losses which they cause unless he has expended large
amounts of capital in providing other ships to take their place on
such occasions of derangement.

Nor is the burning out of heavy brass, and composition, and steel
pieces, or the breaking of large and troublesome parts in the engine
the only source of repairs on a steamship. The boiler department is
particularly fruitful in large bills of repairs, especially if it be
necessary to attain a good mail speed. It stands to reason that if the
whole ship can not be filled with boiler power, which with reasonably
high fires, would give enough steam, then the boilers which are used
must be exerted to their highest capacity, or the rapid speed can not
be attained. Many suppose that the boilers may generate twice the
quantity of steam without any appreciable difference in the wear and
tear; but this is a decided error. For high speed, and what I mean by
high speed is simply that which gives a sufficiently rapid transit to
the mails, the fires must be nurtured up to their highest intensity
and every pound of coal must be burned in every corner of the furnaces
which will generate even an ounce of steam. This continued heat
becomes too powerful for the furnaces and the boilers, and they begin
to oxidize, and burn, and melt away, as would never be the case under
ordinary heat. When the ship comes into port it is found that her
furnaces must be "overhauled," her grate bars renewed, her braces
restored, her boilers patched, sometimes all over, several of their
plates taken out, thousands of rivets removed and supplied, and
probably dozens of tubes also removed and replaced with new ones. But
this is not all. The best boilers can not long run in this way. After
six to seven years at the utmost, they must be removed from the ship
altogether, and new ones must be put into their place. This is also a
most expensive operation. The boilers constitute a large share of the
cost of the engine power. To put a new set of boilers in one of the
Collins steamers will cost about one hundred and ten thousand dollars,
and this must be done every six years. The boilers of the West-India
Royal Mail Steamers, which run very slowly, last on an average, six
years.[A]

[A] Statement by Mr. Pitcher, builder, before the Committee of the
House of Commons. Murray on the _Steam Engine_, p. 170, Second
Edition.

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