purposes. They consist essentially of a chamber through which the
feed-water is passed, and in which it is heated almost to the boiling
point by exhaust steam from the engine. According to the temperature
to which the water is heated in this chamber, and the length of time
required for its passage through the chamber, the carbonates are more or
less completely precipitated, as likewise the matter held in mechanical
suspension. The precipitated matter subsides on shelves or elsewhere in
the chamber, from which it is removed from time to time. The sulphate
of lime, however, and the other soluble salts, and in some cases also a
portion of the carbonates that were not precipitated during the brief
time of passage through the heater, are passed on into the boiler.

Appreciating this insufficiency of existing feed-water purifiers to
effectually remove these dangerous saline impurities, the writer in
designing the feed-water heater now to be described paid special
attention to the separation of all matters, soluble and insoluble; and
he has succeeded in passing the water to the boilers quite free from any
substance which would cause scaling or coherent deposit. His attention
was called more particularly to the necessity of extreme care in this
respect, through the great annoyance suffered by steam users in the
Central and Western States, where the water is heavily charged with
lime. Very simple and even primitive boilers are here used; the most
necessary consideration being handiness in cleaning, and not the highest
evaporative efficiency. These boilers are therefore very wasteful, only
evaporating, when covered with lime scale, from two to three pounds of
water with one pound of the best coal, and requiring cleansing once
a week at the very least. The writer's interest being aroused, he
determined, if possible, to remedy these inconveniences, and accordingly
he made a careful study of the subject, and examined all the heaters
then in the market. He found them all, without exception, insufficient