_a._ The “water piston with fibrous packing” is preferred for many
situations in the West or South, or for water containing grit or mud,
like that of the Ohio River; and, for the comparatively few cases where
pump pressure governors are used, the packed piston will give better
service and longer wear.
_b._ The removable bushing or cylinder in which this piston works must
be of solid bronze.
_c._ As stated in Art. 28 _d_, this bushing should be so constructed as
to be readily interchangeable with the bushing of the inside plunger
type.
_d._ The length of bushing must be such that the ends of piston will
barely come short of the edges of cylinder at contact stroke and not
uncover.
_e._ The thickness of the cylindrical bushings must be not less than is
given in the following table: