differently from the way we advise. We have just stated, that as long
as you have plenty of water, and know you have, there is no danger.
Well, how are you to know? This is not a difficult thing to know,
provided your boiler is fitted with the proper appliances, and all
builders of any prominence, at this date, fit their boilers with from
two to four try-cocks, and a glass gauge. The boiler is tapped in from
two to four places for the try-cocks, the location of the cocks ranging
from a line on a level with the crown sheet, or top of fire box, to
eight inches above, depending somewhat on the amount of water space
above the crown sheet, as this space differs very materially in
different makes of the same sized boiler. The boiler is also tapped on
or near the level of crown sheet, to receive the lower water glass cock
and directly above this, for the top cock. The space between this shows
the safe variation of the water. Don't let the water get above the top
of the glass, for if you are running your engine at hard work, you may
knock out a cylinder head, and don't let it get below the lower gauge,
or you may get your head knocked off.

Now the glass gauge is put on for your convenience, as you can determine
the location of the water as correctly by this as if you are looking
directly into the boiler, provided, the glass gauge is in perfect order.
But as there are a number of ways in which it may become disarranged or
unreliable, we want to impress on your mind that you, must not depend on
it entirely. We will give these causes further on. You are not only
provided with the glass gauge, but with the try-cocks. These cocks are
located so that the upper and lower cock is on or near the level with
the lower and upper end of the glass gauge. With another try-cock about
on a level with the center of glass gauge, or in other words, if the
water stands about the center of glass it will at the same time show at
the cock when tried. Now we will suppose that your glass gauge is in