A.—­The ordinary range of good yellow brass that files and turns well, is about 4-1/2 to 9 ounces of zinc to the pound of copper.  Flanges to stand brazing may be made of copper 1 lb., zinc 1/2 oz., lead 3/8 oz.  Brazing solders when stated in the order of their hardness are:-three parts copper and one part zinc (very hard), eight parts brass and one part zinc (hard), six parts brass, one part tin, and one part zinc (soft); a very common solder for iron, copper, and 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,