ee On the means of safety in Steam Boais. 
boats have to run by night as well as by day, and the practice of pla- 
cing the boilers on the guard platforms, makes it less likely that a se- 
eret leak would be seasonably discovered in any other wa 
Another modification of the principle is, to place the bell outside 
the boiler, and communicate the power of the float to it by the fol- 
lowing means. ‘The tongue instead ef striking immediately on the 
bell, strikes on the end of a rod, communicating (through a packing 
x) to the outside, and in contact with the short arm of a lever, at 
the end of the long arm of which is the hammer ; and this arm may 
be elastic as a spring: the impulse thus given sbibiii the boiler, from 
the float to the rod, gives the blow on the bell outside. 
In this arrangement the blow has to overcome the resistance of the 
packing around the rod, (which is not however much,) and the rod 
has to be returned after the blow, to its place, by hand or by mechan- 
ical means; but this mode permits of a louder alarm; the former 
mode of a warning somewhat more sure. If the bell is external it 
may be so enclosed as to be accessible alone to the captain of the 
boat; if within it is not under the immediate care of either the captain 
or the engineer, but is then independent of human agency, and be- 
comes specially and spontaneously the passengers’ mechanic sentinel. 
or flue boilers the float requires the following modification: The 
depth of water over the flue or furnace may not be sufficient for the 
float. It may, or must in this case, be divided into two parts, con- 
nected across, and of a suitable shape to lay in the deeper water at 
the sides without touching: its connection with the lever will then be 
from the connecting piece. 
The same principle is also applicable to Siacabiaies engines, which 
have hitherto been made with internal flues, and must always proba- 
bly be so; and though the same melancholy consequences in degree, 
are not to be expected in case of explosion, still, some one or two per- 
sons may be exposed to injury. This precaution will not only make 
them also more safe, but more sure of avoiding the damage of rup- 
ture and the inconvenience of delay. 
With sure means of knowing the actual state of the water, steam 
a 
of much higher expansive force may be employed, and more busi- — 
ness done by nearly the same investment of capital. 
Among the advantages of this improvement in steam boilers may 
be also stated, that the circumstance of there being concealed the 
sure means of loud alarm, will make the engineer more vigilant and 
careful, because the occurrence of the occasion for it would show 
gross negligence, unless it were caused by a secret leak and the con- 
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