smaller number give sufficient consideration to the relations which
these items bear to each other, or the manner in which the economy of
any given boiler or engine is affected by the circumstances under which
it is run.

A large number of persons--and they are those who should know better,
too--take for granted that a boiler or engine which is good for one
situation is good for all; a greater error than such an assumption can
scarcely be imagined.

It is true that there are certain classes of engines and boilers which
may be relied upon to give moderately good results in almost any
situation--and the best results should _always_ be desired in
arrangement of a mill--there are a considerable number of details which
must be taken into consideration in making a choice of boilers and
engines.

Take the case of a mill in which it has been supposed that the motive
power could be best exerted by a single engine. The question now is
whether or not it would be best to divide the total power required among
a number of engines.

_First_.--A division of the motive power presents the following
advantages, namely, a saving of expense on lines of shafting of large
diameter.

_Second_.--Dispensing with the large driving belt or gearing, the first
named of which, in one instance under the writer's observation, absorbed
_sixty horse-power_ out of about 480, or about _seven per cent_.