tical rotary pistons, cogged and working into one
another in an air-tight case. The pistons fit close to the inside of the
case, and gear into each on the line of their conjugate diameters. The
action is somewhat similar to the old-fashioned rotary pump, consisting of
two cog wheels in gear with, each other, the spaces at the side of the case
being filled with water, which at the centre are occupied by the teeth in
gear. In Holly's pump, instead of uniform teeth, and depending on the fit
of the teeth with the side of the case and with each other for the packing,
there are two large teeth in each piston opposite each other, which have
slide pistons, and intermediate with these large teeth are small cogs,
which continue the motion of the rotary pistons. The machine works very
smoothly, and performs the work necessary, in ordinary service, under a
pressure of 50 to 60 lbs.

There are many other makers of fire engines in this country; but sufficient
examples are given to illustrate the class; so successful have they been,
that they are fast superseding hand engines, even in the smaller cities.

Under a paid department, the following is, in the city of Boston, Mass.,
the comparative cost of running the two kinds of engines, viz.:

STEAM FIRE ENGINE.
1 engineer........................................... $720 00
1 fireman............................................ 600 00
1 driver............................................. 600 00
1 foreman of hose.................................... 150 00
8 hosemen, at $125 each.............................. 375 00
-- --------
7 men................................................ $2,445 00
Keeping of 2 horses.................................. 315 00
--------
Total......................................... $2,760 00

HAND ENGINE.
1 foreman............................................ $150 00
1 assistant foreman.................................. 125 00
1 clerk.............................................. 125 00
1 steward............................................ 125 00
3 leading hosemen, at $125 each...................... 375 00
33 men, at $100 each................................. 3,300 00
-- ---------
40 men.......................................