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Cast steel has been freely used by the writer for bends, junction
pieces, etc., of steam pipes, as well as for steam valve chests; and
except for the fact that steel makers' promises of delivery are
generally better than their performance, the result has thus far been
satisfactory in all respects. These were adopted because there existed
some doubt as to the strength of gun metal under a high temperature; and
as the data respecting its strength appeared of a doubtful character, a
series of careful tests were made to determine the tensile strength of
gun metal when at atmospheric and higher temperatures. The test bars
were all 0.75 in diameter, or 0.4417 square inch sectional area; and
those tested at the higher temperatures were broken while immersed in a
bath of oil at the temperature here stated, each line being the mean of
four experiments. The result of these experiments was to give somewhat
greater faith in gun metal as a material to be used under a higher
temperature; but as steel is much stronger, it is probably the most
advisable material to use, when the time necessary to procure it can be
allowed.

_Feed Heating_.--With the double object of obviating strain on the
boiler through the introduction of the feed water at a low temperature,
and also of securing a greater economy of fuel, the principle of
previously heating the feed water by auxiliary means has received
considerable attention, and the ingenious method introduced by Mr. James
Weir has been widely adopted. It is founded on the fact that, if the
feed water as it is drawn from the hot well be raised in temperature by
the heat of a portion of steam introduced into it from one of the steam
receivers, the decrease of the coal necessary to generate steam from the
water of the higher temperature bears a greater ratio to the coal
required without feed heating than the power which would be developed in
the cylinder by that portion of steam would bear to the whole power
developed when passing all the steam through all the cylinders. The
temperature of the feed is of course limited by the temperature of the
steam in the receiver from which the supply for heating is drawn.
Supposing, for example, a triple expansion engine were working under the
following conditions without feed heating: Boiler pressure, 150
lb.;--indicated horse power in high pressure cylinder 398, in
intermediate and low pressure c