nd brass, consists of nearly equal parts of
copper and zinc. Muntz's metal consists of forty parts zinc and sixty of
copper; any proportions between the extremes of fifty parts of zinc and
fifty parts copper, and thirty-seven zinc and sixty-three copper, will roll
and work at a red heat, but forty zinc to sixty copper are the proportions
preferred. Bell metal, such as is used for large bells, consists of 4-1/2
ounces to 5 ounces of tin to the pound of copper; speculum metal consists
of from 7-1/2 ounces to 8-1/2 ounces of tin to the pound of copper.

ERECTION OF ENGINES.

719. _Q._--Will you explain the operation of erecting a pair of side lever
engines in the workshop?

A.--In beginning the erection of side lever marine engines in the workshop,
the first step is to level the bed plate lengthways and across, and strike
a line up the centre, as near as possible in the middle, which indent with
a chisel in various places, so that it may at any time be easily found
again. Strike another line at right angles with this, either at the
cylinder or crank centre, by drawing a perpendicular in the usual manner.
Lay the other sole plate alongside at the right distance, and strike a line
at the cylinder or crank centre of it also, shifting either sole plate a
little endways until these two transverse lines come into the same line,
which may be ascertained by applying a straight edge across the two sole
plates. Strike the rest of the centres across, and drive a pin into each
corner of each sole plate, which file down level, so as to serve for points
of reference at any future stage; next, try the cylinder, or plumb it on
the inside roughly, and see how it is for height, in order to ascertain
whether much will be required to be chipped off the bottom, or whether more
requires to be chipped off the one side than the other. Chip the cylinder
bottom fair; set it in its place, plumb the cylinder very carefully with a
straight edge and silk thread, and scribe it so as to bring the cylinder
mouth to the right height, then chip the sole plate to suit that height.
The cylinder must then be tried on again, and the parts filed wherever they
bear hard, until the whole surface is well fitted. Next, chip the place for
the framing; set up the framing, and scribe the horizontal part of the jaw
with the scriber used for the bottom of the cylinder, the upright part
being set to suit the shaft centres, and the angular flange of cylinder,
where th