us. Safety Apparatus for Steam Boats. 
will produce the same dreadful effect. That such circumstances 
have frequently occurred, and have as frequently caused the results 
above described, is fully shown by the various authentic accounts of 
explosions on record. » 
~ The memoir of M. Arago, a translation of which is contained in 
the Journal of the Franklin Institute,* furnishes proofs of this fact; 
and the explosion-of the boiler of the Chief Justice Marshall, during 
the last summer, has, I conceive, been fairlyreferred to the occur- 
rence of similar circumstances. ' 
The French Academy, when called upon, in 1823, to report to 
their government, the precautions to be used to prevent the explo- 
sions of steam boilers, satisfied of the insufficiency of the common 
~ valve to insure safety, required that in addition to two safety valves 
of the ordinary construction, one at the disposal of the engineer, the 
other under lock and key, there should be two plates of fusible 
metal covering apertures in the boiler; the one having its melting 
point at 18°F’. above the temperature of the steam, which, accord- 
ing to'the statement of the proprietor, made when his engine was es 
ished, was required to be used in the engine, the other at 18° 
above the fusing point of the first: the fusing point of each is thus, 
even in a high pressure engine, much below the temperature to which 
the boiler being heated there would be danger of explosion-t Now 
whether the steam be very elastic or not, so soon as it, or the boiler, 
arrives at the temperature requisite to fuse these plates, they melt, 
and the steam is discharged; this, too, below the limit of tempera~ 
ture at which such a discharge of steam would, according to the 
‘statement made in the former part of this article, be attended with i 
"These plates are made of alloys of bismuth, tin, and lead, im pt 
portions varied according to the temperatures at which they are t& 
‘quired to melt; by covering eacl: with a piece of fine wire-gau2% . 
is prevented from swelling out by the effect of softening as it vers® 
towards the fusing point. z: . 
Experience has shown that these plates can be rélied on, confi- 
dently, to answer the ends proposed. . In the stationary engine We 
sich: hin tlle ated. ; ae ee eer 
* Vol. V. No. 6, and Vol. VI, No. 1,1830. t 
t Iron at a dull red heat has a temperature of 947° F. while steam of eleven va 
mospheres corresponds according to the late determination of Arago and went 
o 
a temperature of 367.349 F 
