o the relation between chemical composition and
strength of the material have established that a large amount of
silicium, graphite, manganese, and combined carbon reduce the elasticity,
strength, and tenacity of cast iron, and that a limited percentage of
silicium counteracts the injurious influence produced by an excess of
combined carbon. On remelting of cast iron, increase in tensile strength
was observed, which attained its maximum in iron with a small percentage
of silicium after the third, and in such with a large amount after the
fourth melting. The increase in tensile strength was accompanied by a
loss of silicium, graphite, and manganese coupled with a simultaneous
augmentation of combined carbon. A fifth melting of the cast iron renders
it hard, brittle, and white, through oxidation of silicium and subsequent
lowering of the amount of carbon. On lessening the percentage of combined
carbon with formation of graphite the injurious influence of the
accessorial constituents of cast iron is diminished, especially that
produced by the presence of phosphorus.--_Eisenhuettentechnik._

* * * * *

FEEDING BOILERS AT THE BOTTOM.

One of the most important things to be considered in boiler construction
is the position and arrangement of the feed apparatus, but it is,
unfortunately, one of the elements that is most often overlooked, or, if
considered at all, only in a very superficial manner. Many seem to think
that it is only necessary to have a hole somewhere in the boiler--no
matter what part--through which water may be pumped, and we have all that
is desired. This is a very grave error. Many boilers have been ruined,
and (we make the assertion with the confidence born of long experience) a
large number of destructive explosions have been directly caused by
introducing the feed water into boilers at the wrong point.

On the location and construction of the feed depends to some extent the
economical working of a boiler, and, to a great extent, especially with
certain types of boilers, its safety, durability, and freedom from a
variety of defects, such as leaky seams, fractured plates, and others of
a similar kind. And it is unfortunately true that the type of boiler
which from its nature is most severely affected by mal-construction, such
as we are now speaking of, is the very one which is the oftenest subject
to it. We are speaking now more particularly of the plain cylinder
bo