BOILER AND MANAGEMENT 327 
cock at the bottom is used to blow out the sediment that 
is liable to block the opening between it and the boiler. 
When this occurs the gauge becomes a false indicator. 
Frequent blowing out is therefore necessary. The cock 
next to the blow-out admits the water from the boiler. 
The cock above this admits the steam. When the glass 
breaks shut off the water first, then the steam. Always 
have a few extra glasses on hand so that the broken one 
can be immediately replaced. Owing to its tendency to 
clog, the gauge can not always be relied upon, hence the 
use of water cocks placed next to the glass gauge. 
Water Gauge Cocks: ‘There are three of these used. 
The water level should be kept as near as possible to the 
middle cock. It should never go below the lower cock, 
nor above the upper. These cocks should be opened 
many times during the day, and so long as steam issues 
from the upper and water from the lower cock, the water 
level is all right. 
Steam Gauge. This shows the number of pounds of 
steam pressure per square inch on the boiler by means 
of a pointer moving around a dial. Below the dial is a 
loop which contains water to prevent injury to the gauge 
from the hot steam. The steam gauge is liable to get 
out of order and will then fail to show the true pressure. 
Such a condition is indicated by the safety valve. 
Safety Valve. This is placed on top of the steam 
chamber and permits the escape of steam when the steam 
pressure reaches the danger limit. It is an indispensable 
boiler attachment as without it the boiler would be a 
dangerous thing. There are two kinds of safety valves, 
the “pop” and “ball and lever” types. The former is 
considered the more desirable because it is not so easily 
