elow the level of the injector,
the space within the barrel might be twelve square inches; the water and
steam cocks are supposed to be always open, and this is how the injector
is started working. The water-wheel is turned partly round, and a
figured disc behind it indicates the quantity of water let into the
barrel, while the steam is let in by turning a wheel attached to a
quick-screw spindle; then there are ructions inside--the steam and water
have come together, and the water overflows through the half-inch pipe;
but by a little manipulation of the water, air will soon start it
working; then the overflow ceases, and the air rushes into the pipe and
hums, and the injector is working. And the reason of its working is, in
my humble opinion, the concentration of water and steam, with the vacuum
thrown in, that gives additional pressure to the water in the injector.
I might venture to say it gives fully ten lb. on the square inch over
and above the pressure of steam within the boiler.

25. _Question._--The noise created by the injector while working being
very objectionable, could it be mitigated? And, if so, how?

_Answer._--Yes; I succeeded in quieting an injector in one establishment
where anything louder than the scratching of a goose-quill was
considered a nuisance. I first began by putting a piece of paper against
the mouth of the overflow pipe while the injector was working, and the
noise ceased, but soon after that the paper was sucked up into the
injector. I then applied a leathern disc, which answered well, and
proved just the right thing; sometimes the water blurted out, but not
often, and the leathern disc was permanently established; but the
injector would not work with water above 100 degrees of heat; so I would
start with cold water and gradually turn on the hot water and shut off
the cold, and she never noticed the change, but the noise was stopped.

26. _Question._--How would you quiet a noisy pump--one of those stuck up
in a corner of the stoke-hold that can be heard, but not often seen?

_Answer._--I had one of them once--a very good little "Manchester Donkey
Pump," but as noisy as they make 'em--and it became a question whether
she should be discarded for an injector; she was bolted to a wall in the
basement of a block of offices and could be heard throughout the
building, and my employer told me that he would willingly give a 5_l._
note to anyone who would stop the noise. The donkey was vertic