3. 
= asthe temperature approaches 
: is surrounded by a cylinder, a 
sure, (ten atmospheres,) 
~ closed ‘ih the plate, C, D, of 
; fusible metal, covered by a 
Safety Apparatus for Steam Boats. 321 
=iFig. 1, reptesents an’ > 2 6. s Pig. der ograveses 
oblique view of part of 
a boiler with the safety © 
apparatus attached. An 
unfavorable case, as to 
the space occupied by» 
the apparatus, is taken, 
namely, that of a high 
pressure boiler required 
to work with’ steam of 
150 Ibs. burstmg pres- 
rendering it necessary 
to load the valve with rather more than 150 pounds. 
_ Fig. 2, gives more in detail the method of arranging the fusible 
plate, &c. being a sectionof the apparatus. The area of the aper- 
ture closed by the plate is taken at 3 square inches, which is one 
_ half more than the area of the salety valve eee! used in ahigh 
Pressure boiler of 3 feet in - Fig. 2. SE De 
diameter by 10 feet in length. Eighties 
A, B, Fig. 2. is the aperture 
piece of wire gauze to pre- . 
Vent the plate from yielding © 
point of fusion. The plate 
E, F; G, H, of a greater diameter than the pte ibinated, above, | 
by the valve seat E, F. Should the fusible plate, in giving vent to 
the steam, be thrown upwards, ’ as an expression used by Arago in ~ 
relation to it, gives reason to suppose, the valve should not be in the 
‘eylinder, E, F, G, H, but in one at Ae angles to it, so that the 
Valve seat should not be vertically over the faistbte plate. The valve, 
1K, is represented of the usual form, though it may be questioned, 
whether this is the best which can be given: it is drawn in the posi- 
tion which it should habitually have, that is, ‘so far raised from the 
seat . to see an opening for the escape of steam, equal in area tw 
the va 
